N = int(input()) H = list(map(int,input().split())) iwai = "g" for i in range(N): if len(iwai) < H[i]: while len(iwai) < H[i]: iwai += "g" if iwai[0] == "g": iwai = iwai[:H[i]].replace("g","b") + iwai[H[i]:] else: iwai = iwai[:H[i]].replace("b","g") + iwai[H[i]:] print(iwai.count("b"))