#include <bits/stdc++.h>

using namespace std;

typedef pair<int, int> pii;
typedef long long ll;
const int N = 2000010, MOD = 1e9 + 7, INF = 0x3f3f3f3f;
int n, m, w[N];



int main() {
    cin >> n;
    if (n <= 2) {
        puts("-1");
        return 0;
    }
    printf("%d\n", (n * n) << 1);
    map<int, int> ma;
    for (int i = 1; i <= n * n; i++) {
        int a = i == n * n ? 1 : i + 1, b = i > n * (n - 1) ? i - n * (n - 1) : i + n;
        ma[a] += i, ma[b] += i, ma[i] += a + b;
        printf("%d %d\n%d %d\n", i, a, i, b);
    }
    return 0;
}