백준 #32642번 당구 좀 치자 제발

import java.util.Scanner;
public class Main {
	public static void main(String[] args) {
		
		Scanner sc = new Scanner(System.in);
		
		int n = sc.nextInt();
		int []rain = new int[n];
		int []score = new int[n];
		
		for(int i = 0; i < n; i++) {
			rain[i] = sc.nextInt();
		}
		
		if(rain[0] == 0) {
			score[0] = -1;
		}else {
			score[0] = 1;
		}
		
		for(int i = 1; i < n; i++) {
			if(rain[i] == 0) {
				score[i] = score[i - 1] - 1;
			}else {
				score[i] = score[i - 1] + 1;
			}
		}
		
		long total = 0;
		for(int i = 0; i < n; i++) {
			total += score[i];
		}
		System.out.println(total);
		sc.close();
	}
}