Fixed points

#include<iostream>

using namespace std;

int main(void) {
    int64_t t;
    cin >> t;

    for(;t>0;t--) {
        uint64_t a,b;
        cin >> a >> b;
        uint64_t n=1;
        int64_t iter=0;
        while(iter<1000) {
            uint64_t nn=(a*n)^b;
            if(nn == n) {
                cout << n << "\n";
                break;
            }
            n=nn;
            iter++;
        }
        if(iter==1000) cout << "-\n";
    }
}

Test 1

Verdict: WRONG ANSWER