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

int main(void){

	double vel;
	int N;

	while(scanf("%lf",&vel)!=EOF){
		N=1;
		while(9.8*sqrt((5*N-5)/4.9)<vel){
			N++;
		}
		printf("%d\n",N);
	}

	return 0;
}