#include <iostream>
#include <math.h>
int n;
int main()
{
scanf("%d",&n);
int x = (-2+sqrt(4+8*n))/4;
int a = n-2*x*x-2*x;
int b;
if(a>=0&&a<3) b=0;
else if((a-3)/2<=x-1) b=1+(a-3)/2;
else if(a-3-2*(x-1)>=0&&a-3-2*(x-1)<3) b=x;
else if(a-3-2*(x-1)<5) b=x+1;
else b = x+1+(a-3-2*(x-1)-3)/2;
int y = x*x+b;
if(n<=3) y=0;
printf("%d",y);