#include <bits/stdc++.h>
#define int long long
using namespace std;
int n, m;

void solve () {
    cin>>n;
    cout<<2*n-1<<endl;
    for(int i=1;i<=n;i++){
        cout<<1<<" "<<i*2-1<<endl;
    }
    for(int i=1;i<=n-1;i++){
        cout<<2<<" "<<2*i<<endl;
    }
}
signed main () {
    int T = 1; 
    std::ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
    //cin>>T;
    while (T --) solve ();
    return 0;
}