#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <stack>
#include <queue>
#include <cstring>
#include <climits>
#include <cmath>
#include <cfloat>

using namespace std;

double vn, yn, out, tn;

int main()
{
	
	while( cin >> vn, !cin.eof())
	{
		tn = vn/9.8;
		
		yn = pow(tn, 2) * 4.9;
		
		for( int i = 1; i < INT_MAX; i++)
		{
			int f = 0;
			double flr = (double)(i-1)*5.0;
			
			if( flr >= yn )
			{
				cout << i << endl;
				f = 1;
				break;
			}
			
			if(f)
				break;
		}
		
	}
	
	return 0;
}