def f(x, n):
return sum(map(int, str(x)[-n:]))
print(f(123456789, 1))
print(f(123456789, 2))
print(f(123456789, 3))
print(f(123, 1))
print(f(123, 2))
print(f(123, 3))
print(f(123, 4))
print(f(123, 5))
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