#include <bits/stdc++.h>
using namespace std;

int main() {
    double v, t, y;
    while(cin >> v){
        t = v/9.8;
        y = 4.9*t*t;
        int ans = 1;
        while(double(ans-1)*5<y)ans++;
        cout << ans << endl;
    }
    return 0;
}   

