```
class Solution(object):
def twoSum(self, numbers, target):
"""
:type numbers: List[int]
:type target: int
:rtype: List[int]
"""
i, j = 0, len(numbers)-1
while i < j:
sum = numbers[i] + numbers[j]
if sum == target:
return [i+1, j+1]
elif sum > target:
j -= 1
else:
i += 1
return None
```