#include <bits/stdc++.h>
using namespace std;
#define int long long
int MOD = (int)1e9 + 7;
int INF = (int)2e18;
// Comment out below and program paste

// #include "UnionFind.hpp"
// #include "power.hpp"


int add(int a, int b) {
    return (a + b) % MOD;
}

signed main() {
    int A, B, C, D;
    cin >> A >> B >> C >> D;
    int ans = 0;
    while (true) {
        if (B >= C && D >= (C + 1)) {
            ++ans;
            --A;
            B -= A;
            D -= (C + 1);
        } else {
            break;
        }
    }
    cout << ans << endl;
}