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

int main(void){
while(1){
double a;
cin >> a;
double b = a / (9.8);
double c = b*b*(4.9);
double i = 1;
while(1){
if((5*i-5)>=i) break;
i++;
}
cout << i << endl;
}
return 0;
}