STPAR - Street Parade


For sure, the love mobiles will roll again on this summer's street parade. Each year, the organisers decide on a fixed order for the decorated trucks. Experience taught them to keep free a side street to be able to bring the trucks into order.

The side street is so narrow that no two cars can pass each other. Thus, the love mobile that enters the side street last must necessarily leave the side street first. Because the trucks and the ravers move up closely, a truck cannot drive back and re-enter the side street or the approach street.

You are given the order in which the love mobiles arrive. Write a program that decides if the love mobiles can be brought into the order that the organisers want them to be.

Input

There are several test cases. The first line of each test case contains a single number n, the number of love mobiles. The second line contains the numbers 1 to n in an arbitrary order. All the numbers are separated by single spaces. These numbers indicate the order in which the trucks arrive in the approach street. No more than 1000 love mobiles participate in the street parade. Input ends with number 0.

Output

For each test case your program has to output a line containing a single word "yes" if the love mobiles can be re-ordered with the help of the side street, and a single word "no" in the opposite case.

Example

Sample input:
5
5 1 2 4 3 
0

Sample output:
yes

Illustration

The sample input reflects the following situation:

The five trucks can be re-ordered in the following way:


hide comments
last_mohican: 2017-05-10 13:23:43

Two solutions! The first one (C++) with stacks and the second, more elegant one (Haskell), with no stack at all!

Last edit: 2017-05-10 13:29:11
coder44: 2017-05-06 20:58:07

AC in one go......
Awesome question for learning implementation of stacks...

shauryauppal: 2017-04-13 06:11:18

Use two stacks to solve the problem and try to get answer no first (understand in with cases answer would be no) else print yes.

try tc-5 3 2 1 4 to solve

manishkc: 2017-04-04 21:17:47

AC in one go !!

hamhom2008: 2017-03-20 16:36:37

nice stack problem

lerufic: 2017-03-14 20:55:23

forgot to reset all variables for the next testcases... Finally AC :')

imshubhamk: 2017-02-27 09:32:25

ac.... in one go...

codefirebird: 2017-02-24 07:46:09

Nice problem for learning use of stack.

cat_got_bored: 2017-02-17 21:30:24

One simple WA case :- (5 3 2 1 5 4 , "yes")

sarthaksoni: 2017-02-16 18:39:50

easy one..
AC in a go!!

Last edit: 2017-02-16 18:40:45

Added by:Patryk Pomykalski
Date:2004-07-01
Time limit:1s-2s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: NODEJS PERL6 VB.NET
Resource:Swiss Olympiad in Informatics 2004