main.py

n, k, b = map(int, input().split())

active = [1 for _ in range(n + 1)]
for i in range(b):
    broken = int(input())
    active[broken] = 0

active[0] = 0

answer = 10 ** 9

for i in range(1, n + 1):
    active[i] += active[i - 1]

for i in range(k, n + 1):
    current_active = active[i] - active[i - k]
    answer = min(answer, k - current_active)

print(answer)