#include<cstdio>
#include<cstring>
#include<algorithm>
#include<functional>
using namespace std;
int main(void)
{
	int i,j,y,cnt;
	double n,x,raka;
	while(scanf("%lf",&n)!=EOF) {
		cnt=1;
		x=n/9.8;
		raka=4.9*(x*x);
		i=1;
		while(1) {
			if(5*i-5<raka) cnt++;
			else break;
			i++;
		}
	}
	printf("%d\n",cnt);
	return 0;
}
		