func search(nums []int, target int) int {
    low,high:=0, len(nums) -1
    var mid int
    for low<=high {
        mid = (low+high)/2
        if nums[mid] <target {
            low = mid+1
        }else if nums[mid] > target {
            high = mid - 1
        }else {
            return mid
        }
    }
    return -1
}