N, X, Q = map(int, input().split())
expected = 0.0

for _ in range(Q):
    M = int(input())
    F = list(map(int, input().split()))

    gull_acted = any(f == X for f in F)
    if gull_acted:
        expected += 1.0
        continue

    counts = {}
    multiple = False
    for f in F:
        counts[f] = counts.get(f, 0) + 1
        if counts[f] >= 2:
            multiple = True
            break

    if multiple:
        expected += 0.5

print(f"{expected:.10f}")