solution b

#include<bits/stdc++.h>
using namespace std;

int main()
{
    int n;
    int arr[2*100005+1];
    cin>>n;
    int temp = 0;
    int pos,num = -10;
    for(int i = 0; i < n; i++){
        cin>>arr[i];
        if(num < arr[i]){
            num = arr[i];
            pos = i;
        }
    }
    for(int i = 0; i < (pos-1); i++){
        if(arr[i] > arr[i+1]){
            temp = 1;
            break;
        }
    }
    for(int i = pos+1; i < (n-1); i++){
        if(arr[i] < arr[i+1]){
            temp = 1;
            break;
        }
    }
    if(temp == 1){
        cout<<"NO"<<endl;
    }
    else{
        cout<<"YES"<<endl;
    }
    return 0;
}