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

int main()
{
    int y, t, v, nv, cont = 1;
    cin >> nv;
    
    y = (nv * nv) /19.6;

    while(y>0){	
	y -= 5;
	cont++;
    }
    
    cout << cont << endl;
    
}