class Solution {
public:
    int longestConsecutive(vector<int>& nums) {
        unordered_set<int> num_set;
        for(const int& num: nums)
        {
            num_set.insert(num);
        }

        int longgest = 0;

        for(const int& num : num_set)
        {
            if(!num_set.count(num-1))
            {
                int currentNum = num;
                int currentlong = 1;

                while(num_set.count(currentNum+1))
                {
                    currentNum++;
                    currentlong++;
                }

                longgest = max(longgest,currentlong);
            }

        }

        return longgest;
    }
};