#import numpy as np
import itertools
N = int(input().strip())
A = list(map(int,input().strip().split(' ')))
#Z = np.zeros((N+1,N))
Z = [[0]*int(N+1) for i in range(N) ]
#Z[0,:] = np.array(A)
result = 0

for k in range(N):
        Z[0][k] = A[k]
        if A[k] == 0:
                result = result+1

for i,j in itertools.combinations_with_replacement(range(1,N),2):
        tmp = Z[i-1][j-1]+Z[0][j]
        if tmp ==0:
                result = result+1
        Z[i][j] = tmp
print(result)