#include <iostream>
#include <string>
#include <algorithm>
#include <cstdio>
#include <vector>
#include <cmath>
#include <stack>
#define REP(i, n) for(int i = 0;i < n;i++)
#define REPR(i, n) for(int i = n;i >= 0;i--)
using namespace std;

int main(){
    double n;
    while (cin>>n){
        double t, y;
        t = n / 9.8;
        y = 4.9 * t * t;
        int N;
        N = y / 5 + 2;
        cout << N << endl;
    }
}
