19:2

//integer bisection.
class Solution {
  public:
    int countSquares(int N) {
        N--;
        long long l=0,r=N,ans;
         while(l<=r)
         {
           if(ans*ans>N) break;
          long long mid=(l+r)/2;
          if(mid*mid>N) r=mid-1;
          else
          {

            ans=mid;
            l=mid+1;
           }
         }

        return ans;
    }
};
//fractional bisection
#include<bits/stdc++.h>
using namespace std;
int main()
{
    long long int x;
    cin>>x;
    x--;
    double l=0,r=x;

    for(int i=0;i<100;i++)
    {
       double mid=(l+r)/2.0;
        if(mid*mid>x) r=mid;
        else l=mid;
    }
    cout<<floor(l);
}