class Solution {
public:
    int peakIndexInMountainArray(vector<int>& arr) {
        int l=0;
        int r= arr.size()-1;

        while(l<r){
            int m= l+ (r-l)/2;
            if(arr[m]>arr[m+1]){
                r=m;
            }
            else{
                l=m+1;
            }
        }
        return l;
    
    }
};