N = int(input())
A = list(map(int, input().split()))
A = [0] + A  # Convert to 1-based indexing

current_rev0 = 0
current_rev1 = 0
total = 0

for i in range(N, 0, -1):
    if i == N:
        new_rev0 = 0
        new_rev1 = 0
    else:
        a = A[i]
        if a == 1:
            new_rev0 = 1 + current_rev1
        else:
            new_rev0 = 0
        
        if a == 0:
            new_rev1 = 1 + current_rev0
        else:
            new_rev1 = 0
    
    current_rev0, current_rev1 = new_rev0, new_rev1
    total += current_rev0

print(total)