#include <iostream>
#include <iomanip>
#include <sstream>
#include <stdio.h>
#include <vector>
#include <stack>
#include <queue>
#include <algorithm>
#include <math.h>
#include <utility>
#include <string>
#include <ctype.h>
#include <cstring>
#include <cstdio>
#include <sstream>
#include <functional>

using namespace std;

#define FOR(i,k,n) for(int i = (k); i < (n); i++)
#define REP(i,n) FOR(i,0,n)
#define INF 114514810
#define ll long long
//#define scanf scanf_s

int main()
{
	double n;
	while (cin >> n)
	{
		FOR(i, 1, 114514)
		{
			int h = i * 5 - 5;
			double t = sqrt(h / 4.9);
			double v = 9.8*t;
			if (v > n)
			{
				cout << i << endl;
				break;
			}
		}
	}

	return 0;
}