#include <iostream>
using namespace std;

int main(){
    
    int a, b, c, d,tmp;
    cin >> a >> b >> c >> d;
    while(true){
        tmp = b / c;
        if(tmp + tmp * c < d)
            break;
        b -= c;
    }
    if(a < tmp)
        cout << a << "\n";
    else
        cout << tmp << "\n";
    
    return 0;
}