1494. Монобильярд

1494_monopool.py

n = int(input())
a = []
for _ in range(0, n):
    a.append(int(input()))

stack = []

max_taken = 0
for i in range(0, n):
    if a[i] > max_taken:
        for j in range(max_taken + 1, a[i] + 1):
            stack.append(j)

    last = stack[len(stack) - 1]
    if last == a[i]:
        if stack.pop() > max_taken:
            max_taken = last
    elif last > a[i]:
        print("Cheater")
        break
else:
    print("Not a proof")