i got WA#6 when i use this  code

#include <iostream>
#include <cmath>
using namespace std;

long int n,m,y,p,q,r[999];

int main(){
    cin>>n>>m>>y;
    for (int i=0;i<m;i++){
        if (lround(pow(i,n)) % m==y){
            q++;
            r[q]=i;
        }
    }
    if (q==0){
        cout<<"-1";
    }
    else {
        for (int i=1;i<=q;i++){
            cout<<r[i]<<' ';
        }
    }
}


but when i use neighbored code which is already acc, and tested some test case between them, it give me same results. whats probably wrong in my code

by the way, the neighbored code is pascal language, but the point is, i just used that for test case.