前兩筆測資有通過~
但第三筆被killed，請問該怎麼修改，謝謝

import sys
for line in sys.stdin:
    if line.split():
        n=int(line)
        X={1,2}
        cache=[0 for _ in range(n+1)]
        cache[0]=1
        def staircase(n,X):
            for i in range(n+1):
                cache[i] += (sum(cache[i-x] for x in X if i-x>0))%1000000007
                cache[i] += 1 if i in X else 0
            return cache[-1]
        print(staircase(n,X))