import java.io.BufferedReader;
import java.io.FileReader;
import java.util.Scanner;


public class game {
	public static void main (String[] args) throws Exception{

		BufferedReader in = new BufferedReader ( new FileReader("game.in"));

		String line = in.readLine();
		int b = Integer.parseInt(line);

		while (b!=0){
			
			long z=0;
			
			line = in.readLine();

			int[] arr = new int[b];
			
			Scanner sc = new Scanner(line);
			
			for (int i=0; i<b; i++){
				arr[i] = sc.nextInt();
			}
			
			int i=b-1;
			
			while (i > 0){
				while (arr[i]>0){
					
					arr[i]--;
					
					for (int j=0; j<i; j++){
						arr[j]++;
					}
					z++;
				}
				i--;
				
			}
			
			z=z+arr[0];
			System.out.println(z);
			
			line = in.readLine();
			b= Integer.parseInt(line);
		}

	}
}