Programs always output 0

Programs always output 0

I apologize in advance for any forum etiquette mistakes, this is my first
post up.
Anyways, I have been writing code for the projecteuler.com problems, and
now for the second time a program has, no matter what I do to try and fix
it, returned 0. I'm coding in C.
** PROJECT EULER SPOILER ALERT *******
The first program to have this problem is one that finds the largest
palindrome that can be made by multiplying two numbers of three digits.
/* this is a program to find the largest palindrome produced
by two factors of n digits each */
// test combos of n digit factors for palindrome product
// run backwards to optimize speed for finding largest
// design should work for user input number of digits to be multiplied
#include <stdio.h>
int main()
{
// declare and value vars
int n; // number of digits
int nsub; // for first while loop
int a = 0; // count down 1
int b = 0; // count down 2
int c; // counter
int d; // digit to be moved in palindrome checker algorithm
int e; // translates to true/false for palindrome
int t1; // number to be tested for... (palindromnity? palindromicness?)
int t3 = 0; // just another variable in my palindrome checker
int t4; // aaand another variable
int p; // current leading largest palindrome
// get user input for number of digits
printf("Please input the number of digits (<5 recommended) you \n");
printf("would like in the two factors that will be multiplied \n");
printf("to find the largest palindrome they can produce\n");
scanf("%d", &n);
// translate number of digits to count down start
nsub = n;
while ( nsub > 0 )
{
a = 10 * a + 9;
b = a;
nsub--;
}
int i = a; // random int to avoid 'change in a' problem
// start of finding stuff algorithm
for ( c=0 ; c < i ; c++ )
{
// loop to run through all b vals on one a val
while( b > 0 )
{
t1 = a * b;
// this will allow a check for an any digit palindrome
/* the program will remove the last digit (d) from the
(number that is hopefully a palindrome) and move
it as the first digit in a new number to be compared
to the original. before comparing the numbers with
d moved to the other, it will compare them with d
having been completely removed. this way even and odd
digit palindromes will register correct. */
t4 = t1;
while( t4 > 0 )
{
e = 1;
d = t4 % 10;
t4 = (t4 - d)/10;
if( t4 == t3 )
{
e = 0;
break;
}
t3 = 10 * t3 + d;
if( t4 == t3 )
{
e = 0;
break;
}
}
// e = 0 means it is a palindrome
if(e == 0 && p < t1)
{
p = t1;
// p is the current leading largest palindrome
}
b--;
}
// resets at next a val with equal b val
a--;
b = a;
}
printf("The largest palindrome that is the product\n");
printf("of two numbers of %d digits is: %d\n", n, p);
getchar(); // extra for input
getchar();
return 0;
}
No matter how many digits I use, the program always says my answer is 0.
The next program to have this problem is one that is to find the largest
product of five consecutive digits in a 1000 digit number. This is still a
work in progress.
/*
73167176531330624919225119674426574742355349194934
96983520312774506326239578318016984801869478851843
85861560789112949495459501737958331952853208805511
12540698747158523863050715693290963295227443043557
66896648950445244523161731856403098711121722383113
62229893423380308135336276614282806444486645238749
30358907296290491560440772390713810515859307960866
70172427121883998797908792274921901699720888093776
65727333001053367881220235421809751254540594752243
52584907711670556013604839586446706324415722155397
53697817977846174064955149290862569321978468622482
83972241375657056057490261407972968652414535100474
82166370484403199890008895243450658541227588666881
16427171479924442928230863465674813919123162824586
17866458359124566529476545682848912883142607690042
24219022671055626321111109370544217506941658960408
07198403850962455444362981230987879927244284909188
84580156166097919133875499200524063689912560717606
05886116467109405077541002256983155200055935729725
71636269561882670428252483600823257530420752963450
*/
/* this is a program to find the greatest
product of five consecutive digits in the
1000 digit number above.
*/
#include <stdio.h>
#include <string.h>
int main()
{
char str[1001] =
"73167176531330624919225119674426574742355349194934969835203127745063262395783180169848018694788518438586156078911294949545950173795833195285320880551112540698747158523863050715693290963295227443043557668966489504452445231617318564030987111217223831136222989342338030813533627661428280644448664523874930358907296290491560440772390713810515859307960866701724271218839987979087922749219016997208880937766572733300105336788122023542180975125454059475224352584907711670556013604839586446706324415722155397536978179778461740649551492908625693219784686224828397224137565705605749026140797296865241453510047482166370484403199890008895243450658541227588666881164271714799244429282308634656748139191231628245861786645835912456652947654568284891288314260769004224219022671055626321111109370544217506941658960408071984038509624554443629812309878799272442849091888458015616609791913387549920052406368991256071760605886116467109405077541002256983155200055935729725716362695618826704282524836008232575304
20752963450";
int p; // current product
int g = 0; // current greatest product
int a=5; // counter
while( a != 1001 )
{
str[a]*str[a-1]*str[a-2]*str[a-3]*str[a-4] = p;
if( p > g )
{
g = p;
}
else
{
}
a++;
}
printf("%d is the largest product of five consecutive numbers", g);
getchar();
return 0;
}
Thanks, I have been over it a million times and have no idea what it could
be.