package codeup_100;
import java.util.Scanner;
public class codeup_91 {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int a = sc.nextInt();
int m = sc.nextInt();
int d = sc.nextInt();
int n = sc.nextInt();
int result = a;
for(int i=2; i<=n; i++) {
result = result*m+d;
}
System.out.println(result);
}
}