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

int main(){
    double v;
    while(cin >> v){
        // v = 9.8t
        double t = v / 9.8;
        double y = 4.9*t*t;
        int n = (int)(ceil(y)+4)/5+1; 
        cout << n << endl;
    }
    return 0;
}