class Solution {
public:
    int getNumberSameAsIndex(vector<int>& nums) {
        for(int i=0;i<nums.size();i++)
        {
            int l=0,r=nums.size()-1;
            while(l<r) 
            {
                int mid=l+r>>1;
                if(nums[i]<nums[mid]) r=mid-1;
                else if(nums[i]>nums[mid]) l=mid+1;
                else {l=mid;break;}
            }
            if(l==nums[i]) 
            {
                return nums[i];
            }
        }
        return -1;
    }
};