#include <fstream>

using namespace std;
ifstream f("dame.in");
ofstream g("dame.out");
int main()
{
    int i,j,n;
    f>>n; g<<n<<"\n";
    i=1; j=1;
    while(i<=n)
    {
        g<<i<<" "<<j<<"\n";
        i+=2; j++;
    }
    i=2; j=4;
    while(i<=n)
    {
        g<<i<<" "<<j<<"\n";
        i+=2; j++;
    }
    f.close();
    g.close();
    return 0;
}