Q10515: Power et al.

// Run time: 0.100
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
const int N = 102;
int arr[10] = {1, 1, 4, 4, 2, 1, 1, 4, 4, 2};

int calculate(int m, int n);

int main()
{
   char s[N+1], t[N+1];
   int len1, len2;
   int m, n;
   while (scanf("%s%s", s, t))
   {
       m = atoi(s);
       n = atoi(t);

       if (!m && !n)     break;

       if (!m)
       {
           printf("0\n");
           continue;
       }

       if (!n)
       {
           printf("1\n");
           continue;
       }

       len1 = strlen(s);
       len2 = strlen(t);

       m = s[len1-1] - '0';  // digit in ones
       n = (t[len2-2]-'0')*10 + t[len2-1]-'0';  // digits in ones and tens


       printf("%d\n", calculate(m, n));
   }

   return 0;
}

int calculate(int m, int n)
{
   int i;
   int prod = 1;

   n = n%arr[m] ? n%arr[m] : arr[m];

   for ( i = 0; i < n; i++)
       prod = prod*m;

   return prod%10;
}