#include <iostream>

using namespace std;

int p, n, r;

int main(){
    cin >> p >> n >> r;

    int day = 0, total = n, newp = 0;
    while (total <= p){
        day ++;

        int t = total;
        total += (total - newp) * r;
        newp = t;
    }
    cout << day << endl;

    return 0;
}