#include <iostream>
using namespace std ;

int main()
{
	double get ;
	double high ;
	int sol ;

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

		int tmp = high ;
		if( tmp %5 == 0 )
		{
			sol = high/5 +1 ;
		}
		else
		{
			sol = high/5 +2 ;
		}

		cout << sol << endl ;
	}

	return 0 ;
}