#include <bits/stdc++.h>
using namespace std;
int main(void){
    int n;
    double v,t;
    while (cin >> v) {
        t = v/9.8;
        n = ((4.9*t*t)+5)/5;
        cout << n+1 << endl;
    }
    
    
    
    
    
    
    //4.9*t*t=5*n-5
    //25.4=9.8*t
}
