import java.util.Scanner;

public class Main 
{
    public static void main(String[] args) 
    {
        Scanner input = new Scanner(System.in);
        
        int a = input.nextInt();
        int b = input.nextInt();
        int x = input.nextInt();
        int y = input.nextInt();
        
        int minTurns = Integer.MAX_VALUE;
        int MaxStorms = Math.max(a/y+1,b/y+1);

        for(int storm=0;storm <= MaxStorms;storm++)
        {
            int remainding_a = a - storm*y;
            int remainding_b = b - storm*y;

            int fireballs = 0;
            if(remainding_a > 0)
            {
                fireballs += (remainding_a+x-1)/x;
            }
            if(remainding_b > 0)
            {
                fireballs += (remainding_b+x-1)/x;
            }

            int totalturns = storm + fireballs;
            if(totalturns<minTurns)
            {
                minTurns=totalturns;
            }

        }
        System.out.print(minTurns);

    }
}