This is my code

#include <iostream>

using namespace std;

long long sqr_N(int arg, int Step)
{
    long long Result = 1;
    for(int i=1; i<=Step; i++)
        Result *= arg;
    return Result;
}
int main()
{
    int N,M,Y;
    bool check = false;

    cin >> N >> M >> Y;

    for(int X=0; X<M; X++)
    {
        if(sqr_N(X,N)%M == Y)
        {
            cout << X << ' ';
            check = true;
        }
    }
    if(!check) cout << -1;

    return 0;
}


--------------------------
I can't understand WHY WA#6
Help me somebody

Maximum value of type long long is 2^63-1 less than 998^999