try:
    n = int(input().strip())
    if n < 1 or n > 100:
        print("Invalid input")
    else:
        tasks = []
        for _ in range(n):
            line = input().strip().split()
            if not line:
                print("Invalid input")
                exit()
            tasks.append(set(line))
        common = set()
        all_tasks = []
        for t in tasks:
            for x in t:
                all_tasks.append(x)
        for x in all_tasks:
            if sum(x in t for t in tasks) > 1:
                common.add(x)
        print(*sorted(common)) if common else print("No overlapping tasks")
except:
    print("Invalid input")