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

int main(void) {
    double speed;
    while(cin >> speed) {
        double y = (speed / 2) * (speed / 9.8);
        int n = round((y + 5) / 5.0);
        cout << n << endl;
    }
    return(0);
}