#include<fstream>
using namespace std;
ifstream fi("dame.in");
ofstream fo("dame.out");
int n,i,x,y,d;
int D[]={2,-2};
int main()
{
    fi>>n;
    fo<<n<<"\n";
    x=1;
    y=1;
    d=0;
    for(i=1; i<=n; i++)
    {
        fo<<x<<" "<<y<<"\n";
        x+=D[d];
        y++;
        if(x>n)
        {
            d=1;
            if(n%2==0)
                x--;
            else
                x-=3;
        }
    }
    return 0;
}