#include<iostream>
using namespace std;
int main(){
freopen("p1031.in","r",stdin);
freopen("p1031.out","w",stdout);
int s,n,i,j,k;
cin>>n;
i=1;
s=2;
k=1;
j=1;
while(i<n){
i++;
if (j==2*k-1){
j=1;
s=s+2;
k=k+1;
}else{
j=j+1;
}
}
cout<<s;
fclose(stdin);
fclose(stdout);
return 0;
}
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