n = int(input())
A = list(map(int,input().split()))

groups = []
for i, a in enumerate(A):
    if i == 0:
        prev = a
        cnt = 1
        continue
    if a != prev:
        groups.append(cnt)
        prev = a
        cnt = 1
    else:
        cnt += 1
groups.append(cnt)

#print(groups)

tmp = 0
tmp2 = 0
for i in range(0,len(groups),2):
    tmp += groups[i]
for i in range(1,len(groups),2):
    tmp2 += groups[i]
    
print(max(tmp, tmp2))