/**
knakul853
**/
class Solution {
public:
    int longestConsecutive(vector<int>& nums) {

        int n = (int)nums.size();
        unordered_map<int, int>st;
        for(int c: nums)st[c]++;

        int ans = 0;

        for(int i=0;i<n;i++)
        {
            int num = nums[i];
            if( !st.count(num-1) )
            {
                int cnt=1;
                while(st.find(++num) != st.end())cnt++;

                ans = max(ans, cnt);
            }
        }
        return ans;

    }
};