using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Write the, initial offer, raise value, driver's offer, and reduction value, separated by spaces: ");

        string input =Console.ReadLine();

        string[] inputArray = input.Split(' ');

        int petrOffer = int.Parse(inputArray[0]);

        int raise = int.Parse(inputArray[1]);

        int driverOffer = int.Parse(inputArray[2]);

        int reduction = int.Parse(inputArray[3]);

        while(petrOffer < driverOffer)

        {

            petrOffer +=raise;

            driverOffer -= reduction;

        }

        Console.WriteLine("Petr will pay: " + petrOffer);

    }

}