import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int n = Integer.parseInt(br.readLine());
		String[] sa = br.readLine().split(" ");
		int[] b = new int[n];
		for (int i = 0; i < n; i++) {
			b[i] = Integer.parseInt(sa[i]);
		}
		br.close();

		long ans = 0;
		int j = 0;
		for (int i = 0; i < n; i++) {
			while (b[j] == 0) {
				j++;
			}
			ans += Math.abs(i - j);
			b[j]--;
		}
		System.out.println(ans);
	}
}