Hacker Rank Euler's Criterion

#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstring>

#define sf scanf
#define pf printf
#define limit 32000

using namespace std;

typedef long long LL;


LL bigmod(LL a, LL b , LL c)
{
    if(!b) return 1;

    if(!(b&1))
    {
        LL r = bigmod(a, b/2, c);
        return ((r%c) * (r%c))%c;
    }

    else
    {
        return ((a%c) * (bigmod(a, b-1, c)%c))%c;
    }
}

bool isQuadratic_residue(LL n, LL p)
{
    if(bigmod(n, (p-1)/2 , p) == 1) return true;
    else return false;
}

int main()
{
    int t;
    sf("%d", &t);
    while(t--)
    {
        LL a,m;
        sf("%lld %lld", &a, &m);

        if(isQuadratic_residue(a,m) or a==0) pf("YES\n");

        else pf("NO\n");
    }

    return 0;
}