#include <bits/stdc++.h>
using namespace std;
const int N = 366;
int a[N];
int sum;
int main() {
    cin >> a[1] >> a[2]; // 第一天a[1]道题，第二天a[2]道题
    int n, m;
    cin >> m >> n;
    sum += a[1], sum += a[2];
    for (int i = 3;; i++) {
        a[i] = a[i - 1] + a[i - 2];
        if (a[i] >= m) break;
        sum += a[i];
    }
    cout << sum << endl;
    return 0;
}