NEED TO UNDERSTAND

bigmod.c

#include <stdio.h>

int bigmod(int a, int p, int m)
{
    int res = 1;
    int x = a;
    while(p) {
        if(p&1) //odd
            {
                res =(long long) (res*x)%m;
            }
            //even
        x = (x*x)%m;
    p>>=1;  //Divide by two using right shift by 1
    }
    return res;
}

int main() {
    int hello = bigmod(57,153,11);
    printf("%d",hello);
    return 0;
}