// based on k.inaba's code in the D language

using System;
using System.Collections.Generic;
using System.IO;

public class BalanceTheTree {
	private static int[] ReadCase(StreamReader sr) {
		string[] s = sr.ReadLine().Split(' ');
		int n = int.Parse(s[0]);
		int[] a = new int[n];
		for(int i = 0; i < n; i++) a[i] = int.Parse(s[i+1]);
		return a;
	}

	private static bool Solve(int[] a) {
		Stack<int> stack = new Stack<int>();

		for(int i = a.Length - 1; i > 0; i--) {
			if(stack.Count == 0)
				stack.Push(a[i]);
			else {
				if(a[i] < stack.Peek()) { stack.Push(a[i]); continue; }
				if(a[i] > stack.Peek()) return false;
				a[i-1] += a[i];
				stack.Pop();
			}
		}

		return stack.Count == 0;
	}

	public static void Main() {
		using(StreamReader sr = new StreamReader("balance.in")) {
			int[] a;
			while((a = ReadCase(sr)).Length > 0) {
				Console.WriteLine(Solve(a) ? "yes" : "no");
			}
		}
	}
}