class Solution {
    public int longestConsecutive(int[] nums) {
        if(nums.length==0)
            return 0;
        HashSet<Integer>set=new HashSet<Integer>();
        for(int num:nums)
        {
            set.add(num);
        }
        int ans=1;
        for(int num:nums)
        {
            int count=1;
            if(!set.contains(num-1))
            {
                while(set.contains(num+1))
                {
                    num++;
                    count++;
                }
                ans=Math.max(num,count);
            }
        }
        return ans;
    }
}