//
// FILE: binsqrt.cpp
// Author: Leo Reyzin
// Purpose: code to take in an integer and find its integer square root
// HW3 of CS112B1 Spring 2003
//
#include<iostream>
using namespace std;

// Outputs the integer square root of x, that is,
// the largest integer y such that y*y<=x.
// For example, binsqrt(0)=0, binsqrt(5)=2, binsqrt(9)=3.
unsigned int binsqrt(unsigned int x) 
{
  unsigned int low=0, high=x+1, mid;

  // invariant: at the beginning of each loop iteration
  // high must always be greater than the real
  // square root of x, while low must always be less than or equal
  // to the real square root of x.
  // This is why high is set to x+1 above -- else, for x=0 or 1,
  // it would be equal to sqrt x, not greater than
  while (low<high-1) {
    mid = (low+high)/2; // take the average, possibly rounded down
    if (mid*mid > x)
      high = mid; // Note that high remains greater than the real root of x
    else 
      low = mid;  // Note that low remains less than or equal to real root of x
  }
  // We are now guaranteed that high=low+1, and the real root of x
  // is in the interval [low,high[ So low is the right thing to output
  return low;
}

int main()
{
  unsigned int x;
  cin >> x;
  cout << binsqrt(x) <<'\n';
  return 0;
}