63B - Settlers' Training - CodeForces Solution

n , k = map(int ,input().split())
m = list(map(int ,input().split()))
counter = 0 
while sum(m) < k*n:
    visted = [0] * (k + 1)
    for i in range(n) : 
        if visted[m[i]] == 0 and m[i] < k:
            visted[m[i]] = 1
            m[i] += 1
    counter += 1
print(counter)