codeforces 392A Blocked Points

#include<iostream>
#include<cmath>
#include<cstring>
using namespace std;

int main()
{
    long long n;
    cin>>n;
    if(n==0){cout<<1;return 0;}
    long long pre=0,cur;
    long long ans=0;
    for(long long i=0;i<=n;i++)
    {
        cur=(long long)(sqrt(1.0*(n*n-i*i)));
        ans++;
        if(pre-cur>1)
            ans+=pre-cur-1;
        pre=cur;
    }
    ans--;
    cout<<ans*4;
}