CD

TLE

# https://open.kattis.com/contests/k6guuj/problems/cd

while True:
    n, m = map(int, input().split())
    if n == 0 and m == 0:
        break

    a = set()
    b = set()
    for i in range(n):
        a.add(int(input()))
    for i in range(m):
        b.add(int(input()))

    print(len(a & b))

Use stdin

It’s faster than input()

# https://open.kattis.com/contests/k6guuj/problems/cd
import sys

while True:
    n, m = map(int, sys.stdin.readline().split())
    if n == 0 and m == 0:
        break

    a = set()
    b = set()
    for i in range(n):
        a.add(int(sys.stdin.readline()))
    for i in range(m):
        b.add(int(sys.stdin.readline()))

    print(len(a & b))