N,K,B = map(int,input().split())
D = [0]*(N+1)
for i in range(B):
D[int(input())] = 1
ans = N+1
S = 0
for i in range(1,K+1):
S += D[i]
if S < ans:
ans = S
for i in range(1,N-K+1):
S -= D[i]
S += D[i+K]
if S < ans:
ans = S
print(ans)