Find first and Last position of Element in sorted array

class Solution {
public:
    vector<int> searchRange(vector<int>& nums, int target) {
        vector<int> ans;
        vector<int>::iterator l, r;
        l=lower_bound(nums.begin(),nums.end(),target);
        r=upper_bound(nums.begin(),nums.end(),target);
        if(l==nums.end() || nums[l-nums.begin()]!=target || l==r){
            ans.push_back(-1);ans.push_back(-1); return ans;
        }
        ans.push_back(l-nums.begin());
        ans.push_back(r-nums.begin()-1);
        return ans;
    }
};