#include<bits/stdc++.h>
#define int long long
#define endl '\n'
using namespace std;
void solve()
{
    int n,num=0;
    cin>>n;
    cout<<2*n<<endl;
    for(int i=1;i<=2*n;i++)
    {
        cout<<i<<' '<<1<<endl;
    }
}
signed main()
{
    cin.tie(0)->sync_with_stdio(0);
    int t=1;
    // cin>>t;
    while(t--) solve();
    return 0;
}