#include<iostream>
#include<math.h>

using namespace std;

int main() {
    double k;
    double current = 0.000000;
    cin >> k;
    int count = 1;
    while (true) {
        current = current + 2.000000 * pow(0.98, count - 1);

        if (current >= k) {
            cout << count << endl;
            break;
        }
        count++;
    }

    return 0;
}