class Solution {

public:

    void backTrack(vector<int> ans, vector<int> nums, vector<vector<int>>& res, int times,int k)

    {

        if(ans.size() == k)

        {

            res.push_back(ans);

        }

        else

        {

            for(int i = times; i<nums.size(); i++)

            {

                ans.push_back(nums[i]);

                backTrack(ans,nums,res,i+,k);

                ans.pop_back();

            }

        }

    }

    vector<vector<int>> combine(int n, int k) {

        vector<vector<int>> res;

        vector<int> ans;

        vector<int> nums;

        for(int i=;i<=n;i++)

            nums.push_back(i);

        int bgi = ;

        backTrack(ans,nums,res,bgi,k);

        return res;

    }

};