find the frequency

class Solution {
public:
    vector<int> searchRange(vector<int>& nums, int target) {
        int l=lower_bound(nums.begin(),nums.end(),target)-nums.begin();
        int u=upper_bound(nums.begin(),nums.end(),target)-nums.begin();
        if(l==u) return {-1,-1};
        else return{l,u-1};
    }
};