// https://omegaup.com/arena/problem/Conjunto-Capicua 
#include <stdio.h> 
 
int main( ) { 
   int n; 
   scanf("%d", &n); 
   int a[n]; 
 
   for (int i = 0; i < n; ++i) { 
      scanf("%d", &a[i]); 
   } 
 
   int dedo = 1; 
   for (int i = 0, j = n - 1; i < j; ++i, --j) { 
      if (a[i] != a[j]) { 
         dedo = 0; 
         break; 
      } 
   } 
 
   printf((dedo == 1 ? "SI" : "NO")); 
}