class Solution {
public:
    int longestConsecutive(vector<int>& nums) {
        unordered_map <int, int> data;
        for(int x:nums) data[x] = 1;
        int res = 0;
        for(auto &n:data){
            if(n.second){
                int val = n.first; int len = 1;
                for(int i = 1; data.count(val - i)&&data[val - i]; i++){
                    data[val - i] = 0; len++;
                }
                for(int i = 1; data.count(val + i)&&data[val + i]; i++){
                    data[val + i] = 0; len++;
                }
                res = max(len, res);
            }
        }
        return res;
    }
};