#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <functional>
#include <numeric>
#include <stack>
using namespace std;

#define FOR(i,a,b) for(long long int i=(a);i<(b);i++)
#define REP(i,n) for(long long int i=0;i<(n);i++)
#define ALL(s) (s).begin(),(s).end()

#define PI 3.14159265358479

typedef long long ll;
typedef vector<long long int> vi;
typedef vector<long long int>::iterator vit;

int main(){
	double v;
	while (cin >> v){
		for (int i = 0;;i++){
			if (v < 9.8*sqrt((5 * i - 5) / 4.9)){
				cout << i << "\n";
				break;
			}
		}
	}
}