#include <iostream>
#include <cmath>
using namespace std ;

int main()
{
	double get ;
	double high ;

	while( cin >> get )
	{
		high = 4.9 *(get/9.8)*(get/9.8) ;

		int i = ceil( high/5 ) ;
		cout << i+1 << endl ;
	}

	return 0 ;
}