ZYB建围墙

#include <iostream>
#include <cstdio>
using namespace std;
long long n,k=0,ans;
int main()
{
	scanf("%lld",&n);
	if(n==0) {cout<<0<<endl; return 0;}
	for(k=1;;++k)
		if(k*(k-1)*3+1>=n) {--k; break;}
	n=n-1-k*(k-1)*3;
	if(k-1>=n) ans=1;
	else if(2*k-1>=n) ans=2;
	else if(3*k-1>=n) ans=3;
	else if(4*k-1>=n) ans=4;
	else if(5*k-1>=n) ans=5;
	else ans=6;
	cout<<ans+k*6<<endl;
	return 0;
}