N = int(input())
A = list(map(int, input().split()))
A[-1]=0
ans = 0
k = 0
for i in range(N-1):
    if (k==0 and A[i]==0):
        continue
    if (k>0 and A[i]==A[i-1]):
        for j in range(k,0,-2):
            ans+=j
        k=A[i]
    else:
        k+=1
for i in range(k,0,-2):
    ans+=k
print(ans)