//何階から落とす？
#include<cstdio>
#include<cmath>

using namespace std;

int main(void){
	double in,y,h,t;
	int ans;

	while(scanf("%lf",&in)==1){
		t=in/9.8;
		y=4.9*(t*t);
		h=(y+5)/5;
		ans=ceil(h);
		printf("%d\n",ans);
	}

	return 0;
}