#include <cstdio>
#include <cmath>

using namespace std;

int main(void){
	int n;
	double mv;
	while(scanf("%lf",&mv) != EOF){
		for(n = 1;sqrt(19.6 * (5 * n - 5)) < mv;n++);
		printf("%d\n",n);
	}
	return 0;
}