a, b, c = map(int, input().split())

for x in range(4):
    temp = [a, b, c, x]
    counts = [0] * 4
    for num in temp:
        counts[num] += 1
    
    # Check condition 1: all same
    cond1 = any(cnt == 4 for cnt in counts)
    
    # Check condition 2: exactly two types each appearing twice
    freq = {}
    for cnt in counts:
        if cnt > 0:
            freq[cnt] = freq.get(cnt, 0) + 1
    cond2 = freq == {2: 2}
    
    # Check condition 3: all distinct
    cond3 = all(cnt <= 1 for cnt in counts) and (sum(counts) == 4)
    
    if cond1 or cond2 or cond3:
        print(x)
        break