import std.stdio;
import std.string;
import std.conv;
import std.math;



int main()
{
	string s;
	while((s=readln.chomp).length != 0)
	{
		double value = s.to!double;
		double min_t = value/9.8;
		double just = 4.9*min_t*min_t;
		int number = cast(int)((just+10)/5.0);
		writeln(number);
	}
	return 0;
}