#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) {
		rep(i, 1000) {
			double y = 5 * i - 5;
			double t = sqrt(y / 4.9);
			double a = 9.8 * t;
			if(a > v) {
				printf("%d\n", i);
				break;
			}
		}
	}
	return 0;
}