#include <bits/stdc++.h>
using namespace std;

int a,b,c,d,i,x = 0,i2 = 0;

int main(){
    scanf("%d %d %d %d",&a,&b,&c,&d);
    if(a * c <= b && a + (a * c) <= d){
        printf("%d\n", a);
        return 0;
    }
    for(i = a; i * c >= b; i--){
        x = i;
    }
    while( x + (x * c) > d || x * c > b){
        x--;
    }
    if(x * c > b){
        printf("%d\n", 0);
        return 0;
    }
    printf("%d\n",x);
    return 0;
}