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

using namespace std;

double v, y, out, t;

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