#include <iostream>
#include <string>
#include <math.h>
#include <stdio.h>
#include <ctype.h>

using namespace std;

int main() {
    double v;
    
    while((cin>>v)){
        double t = v/9.8;
        double y = 4.9*t*t;
        double h = (y + 5.0)/5.0;
        cout<<ceil(h)<<endl;
    }
    return 0;
}