#include <iostream>
using namespace std;

int main(){
    double v;
    double y;
    int n = 1;

    while(cin >> v){
        y = (v * v) / (2.0 * 9.8);
        while(y >= 5 * n - 5){
            n++;
        }
        cout << n << endl;
    }

    return 0;
}