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;
        bool fail=true;
        for(int64_t tries=0;tries<1000;tries++) {
            uint64_t n=rand()*rand();
            int64_t iter=0;
            while(iter<100) {
                uint64_t nn=(a*n)^b;
                if(nn == n) {
                    cout << n << "\n";
                    break;
                }
                n=nn;
                iter++;
            }
            if(iter!=100) {
                fail=false;
                break;
            }
        }
        if(fail)
                cout << "-\n";
    }
}

Test 1

Verdict: TIME LIMIT EXCEEDED