#include <bits/stdc++.h> using namespace std; const int N = 25; bool col[N] , zhu[N] , fu[N]; int ans; int n; void dfs(int x) { if(x == n + 1) { ans++; return; } for(int i = 1;i <= n;i++) { if(!col[i] && !zhu[x + i - 1] && !fu[x - i + n]) { col[i] = zhu[x + i - 1] = fu[x - i + n ] = 1; dfs(x + 1); col[i] = zhu[x + i - 1] = fu[x - i + n] = 0; } } } int main() { cin >> n; dfs(1); cout << ans; return 0; }