#include<iostream>
#include<math.h>
#include<algorithm>
#define lli long long int

using namespace std;

//checks whether current number of students can be given the tokens...
bool check(lli ans, lli m, lli x) {
    lli temp = 0;
    for (lli i = 0; i < ans; i++) {
        if (temp + x <= m)
            temp += x;
        else {
            return false;
        }
    }
    return true;
}

int main() {
    lli n, m, x, y;
    cin >> n >> m >> x >> y;

    lli low = 0, high = n , ans = 0, newm;
    while (low <= high) {
        lli mid = (low + high) / 2;
        if (check(mid, m, x)) {
            //new tokens = tokens we had + tokens by money from non qualifying students...
            newm = ((n - mid) * y) + m;
            ans = newm / x;
            low = mid + 1;
        }
        else
            high = mid - 1;
    }

    cout << ans;
}