#include<iostream>
using namespace std;
int main()
{
    double sum = 0, s;
    int  p = 0;
    cin >> s;

    for (int i = 1;sum < s;i++)
    {
        if (i == 1)
        {
            sum = 2;
            p++;
        }
        else
        {
            sum += 0.98 * sum;
            p++;
        }
    }
    cout << p;

    system("pause");

    return 0;
}