#include <bits/stdc++.h>   int n, a[200005];   bool check1(int x) {     for (int i = x + 1; i <= n; i++)       if (a[i] >= a[i - 1]) return 0;     return 1;   }   bool check2(int x) {     for (int i = x + 1; i <= n; i++)       if (a[i] <= a[i - 1]) return 0;     return 1;   }   int main() {     scanf( %d , &n);     for (int i = 1; i <= n; i++) scanf( %d , &a[i]);     if (check1(1) || check2(1)) {       printf( YES );       return 0;     }     for (int i = 2; i <= n; i++) {       if (a[i] <= a[i - 1]) {         if (check1(i))           printf( YES );         else           printf( NO );         return 0;       }     }     return 0;   }   