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".