CompetitiveProgramming/src/bin/testgen.cc

#include<bits/stdc++.h>
using namespace std;

int main() {
    cout << 1 << endl << 200000 << endl;
    for (int i = 0; i < 199999; ++i) {
        cout << i + 1 << ' ' << i + 2 << endl;
    }
}