ABC-368 B - Decrease 2 max elements

def getInt():
    return int(input())
 
 
def getIntList():
    return list(map(int, input().split()))
 
 
def checker(x):
    return len([i for i in x if i > 0])
 
 
def main():
    N = getInt()
    A = getIntList()
 
    c = 0
    while checker(A) > 1:
        A.sort()
        for i in range(N - 2, N):
            A[i] -= 1
        c += 1
    print(c)
 
 
if __name__ == "__main__":
    main()