C :

#include <stdio.h>

int main()
{
    int a,b,c;
    while(~scanf("%d%d%d",&a,&b,&c))
    {
        int d[100],r=a,s=1,i=0;
        while(b)
        {
            d[i++]=b%2;
            b>>=1;
        }
        for(int k=i-1;k>=0;k--)
        {
            s=(s*s)%c;
            if(d[k]==1)
                s=(s*a)%c;
        }
        printf("%d\n",s);
    }

  return 0;
}

C++ :

# include <iostream>
using namespace std;
int a,b,c,s;
int ans(int a,int b){
    if (b==1) return a%c;
    int t = ans(a,b/2);
    t = ( t * t ) % c;
    if (b & 1) return t*a%c;
    return t%c;
}
int main(){
    for (;cin >> a >> b >> c;cout << ans(a%c,b) << endl) ;
    return 0;
}