n = int(input()) data = [] for i in input().strip().split(" "): data.append(int(i)) cus = 0 res = 0 while cus <= n-1: #print(cus) if cus == n-1: if data[cus]==0: res +=1 break if data[cus] == 0: cus +=1 res +=1 elif data[cus] == data[cus +1]: cus +=2 res +=1 else: cus +=1 print(res)