A. Possible Subscribers

Input file: standard input Output file: standard output Time limit: 1 second Memory limit: 256 megabytes

MegaMath Channel starts at 0 subscribers. Every day i, the channel gains xi subscribers. Help MegaMath determine whether this is a possible sequence of values of xi (the total number of subscribers must stay ≥ 0.)

Input

The first line contains the number of days n (1 <= n <= 100). The next n lines contain a single integer xi.

Output

Print "Yes" if the total number of subscribers MegaMath Channel has is, at any given day, >= 0. Otherwise, print "No".