class Solution {

public:

    int GetNumberOfK(vector<int> data ,int k) {

        if(data.empty())

            return ;

        int First = getFirstofK(data,k);

        int Last = getLastofK(data,k);

        if(First == - || Last == -)

            return ;

        else

            return Last - First + ;

    }

    int getFirstofK(vector<int> data,int k){

        int length = data.size();

        int begin = ;

        int end = length - ;

        while(begin <= end){

            int mid = (begin + end)/;

            if(data[mid] == k){

                if(data[mid-] != k)

                    return mid;

                else

                    end = mid - ;

            }

            else if(data[mid] < k)

                begin = mid + ;

            else

                end = mid - ;

        }

        return -;

    }

    int getLastofK(vector<int> data,int k){

        int length = data.size();

        int begin = ;

        int end = length - ;

        while(begin <= end){

            int mid = (begin + end)/;

            if(data[mid] == k){

                if(data[mid+] != k)

                    return mid;

                else

                    begin = mid + ;

            }

            else if(data[mid] < k)

                begin = mid + ;

            else

                end = mid - ;

        }

        return -;

    }

};