BCQUEEN - N - Queen

include <bits/stdc++.h>
using namespace std;
int n,s,c[20],c1[50],c2[50];
void Try(int x){
	if(x==n+1){
		s++;
		return;
	}
	for(int i=1;i<=n;i++){
		if(c[i]==0&&c1[i+x]==0&&c2[x-i+n]==0){
			c[i]=1;
			c1[i+x]=1;
			c2[x-i+n]=1;
			Try(x+1);
			c[i]=0;
			c1[i+x]=0;
			c2[x-i+n]=0;
		}
	}
}
int main(){
	s=0;
	for(int i=0;i<20;i++) c[i]=0;
	for(int i=0;i<50;i++){
		c1[i]=0;
		c2[i]=0;
	}
	cin>>n;
	Try(1);
	cout<<s;
}