#include <bits/stdc++.h>

using namespace std;

#define FOR(i, j, k) for(int i = j; i < k; ++i)
#define rep(i, j) FOR(i, 0, j)
#define repr(i, j) for(int i = j; i >= 0; --i)
#define INF (1 << 30)
#define MOD 1e9 + 7

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> P;

int num[5000];

int main() {
	double v;
	while(scanf("%lf", &v) != EOF) {
		double t = v / 9.8;
		double y = 4.9 * t * t;
		double N = (y + 5.0) / 5.0;
		double tmp = N * 1000000.0;
		int a = (int)tmp;
		//cout << a << endl;
		if(a % 10 == 0) printf("%d\n", a / 1000000);
		else printf("%d\n", a / 1000000 + 1);
	}
	return 0;
}