#include <bits/stdc++.h>   const double Pi = 3.14159265;   const int N = 1e6 + 50;   const int M = 1e5 + 15;   const unsigned long long base = 163;   const int INF = 0x3f3f3f3f;   using namespace std;   int a[N];   int main() {     int n;     scanf( %d , &n);     int l = 0, r = 0;     for (int i = 1; i <= n; i++) {       cin >> a[i];     }     int pre = 1;     int now = -1;     int flag = 0;     for (int i = 1; i <= n - 1; i++) {       if (a[i] == a[i + 1]) {         pre++;       } else {         flag = 1;         if (now == -1)           now = pre;         else {           if (pre != now) {             cout <<  NO  << endl;             return 0;           }         }         pre = 1;       }     }     if (pre != now && flag) return cout <<  NO n , 0;     cout <<  YES  << endl;     return 0;   }   