#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
using namespace std;
int main(){
    double vm;
    while(cin>>vm){
        double t,y;
        t = vm/9.8;
        y = 4.9*t*t;
        int i=1;
        while(y>5*i-5) i++;
        cout<<i<<endl;
    }
}