#include <iostream>
#include <fstream>

using namespace std;

ifstream f("dame.in");
ofstream g("dame.out");

int v[1010],n;
bool finish;

bool valid(int k)
{
    for(int i = 1; i < k; i++){
        if(v[i] == v[k])
            return 0;
        if(v[i] - v[k] == k - i || v[i] - v[k] == i - k)
            return 0;
    }
    return 1;
}
void bak(int k)
{
    for(int i = 1; i <= n && finish == false; i++){
        v[k] = i;
        if(valid(k)){
            if(k == n){
                finish = true;
                g << n << "\n";
                for(int j = 1; j <= n; j++)
                    g << j << " " << v[j] << "\n";
            } else {
               bak(k+1);
            }
        }
    }
}

int main()
{
    f >> n;
    bak(1);
    return 0;
}