#include <bits/stdc++.h>

using namespace std;

int main() {
    float x;
    cin >> x;
    float pre = 2;
    float sum = 2;
    for (int i = 2;; i++) {
        sum += pre * 0.98;
        pre = pre * 0.98;
        if (sum > x) {
            cout << i << endl;
            break;
        }
    }
    return 0;
}