class Solution {
    public int longestConsecutive(int[] nums) {
        HashSet<Integer> set = new HashSet<>();
        for(int x: nums) set.add(x);

        int res = 0;
        for(int i: nums)
            if(set.contains(i) && !set.contains(i - 1)){
                set.remove(i);
                int j = i;
                while(set.contains(j + 1))
                    set.remove(++ j);
                res = Math.max(res, j - i + 1);
            }

        return res;
    }
}