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

int main() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    cout << 99 << "\n";
    for (int i = 1; i <= 99; i++) {
        cout << i << " " << i + 1 << "\n";
    }
    return 0;
}