
#define _USE_MATH_DEFINES
#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cmath>
#include <string>
#include <cstring>
#include <vector>
#include <map>
#include <utility>
#include <complex>
#include <stack>
#include <climits>

using namespace std;

double sq(double x){return x*x;}

int a[5001];

int main(){
	double d;
	while(cin>>d){
		d = sq(d / 9.8) * 4.9 + 5;
		int n = (int)(d / 5);
		if((double)n * 5 != d)
			n++;
		cout << n << endl;
	}

	return 0;
}