#include <iostream>
using namespace std;
int main() {
	double n;
	cin >> n;
	double x = 2.0, d = 2.0;
	for (int i = 1;i<n; i++) {
		if (d >= n) {
			cout << i;
			break;
		}
		d += (x * 0.98);
	}
	return 0;
}