CF555E.Case of Computer Network

普及/提高-

通过率:0%

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题目描述

Andrewid the Android is a galaxy-known detective. Now he is preparing a defense against a possible attack by hackers on a major computer network.

In this network are nn vertices, some pairs of vertices are connected by mm undirected channels. It is planned to transfer qq important messages via this network, the ii -th of which must be sent from vertex sis_{i} to vertex did_{i} via one or more channels, perhaps through some intermediate vertices.

To protect against attacks a special algorithm was developed. Unfortunately it can be applied only to the network containing directed channels. Therefore, as new channels can't be created, it was decided for each of the existing undirected channels to enable them to transmit data only in one of the two directions.

Your task is to determine whether it is possible so to choose the direction for each channel so that each of the qq messages could be successfully transmitted.

输入格式

The first line contains three integers nn , mm and qq ( 1<=n,m,q<=21051<=n,m,q<=2·10^{5} ) — the number of nodes, channels and important messages.

Next mm lines contain two integers each, viv_{i} and uiu_{i} ( 1<=vi,ui<=n1<=v_{i},u_{i}<=n , viuiv_{i}≠u_{i} ), that means that between nodes viv_{i} and uiu_{i} is a channel. Between a pair of nodes can exist more than one channel.

Next qq lines contain two integers sis_{i} and did_{i} ( 1<=si,di<=n1<=s_{i},d_{i}<=n , sidis_{i}≠d_{i} ) — the numbers of the nodes of the source and destination of the corresponding message.

It is not guaranteed that in it initially possible to transmit all the messages.

输出格式

If a solution exists, print on a single line "Yes" (without the quotes). Otherwise, print "No" (without the quotes).

输入输出样例

  • 输入#1

    4 4 2
    1 2
    1 3
    2 3
    3 4
    1 3
    4 2
    

    输出#1

    Yes
    
  • 输入#2

    3 2 2
    1 2
    3 2
    1 3
    2 1
    

    输出#2

    No
    
  • 输入#3

    3 3 2
    1 2
    1 2
    3 2
    1 3
    2 1
    

    输出#3

    Yes
    

说明/提示

In the first sample test you can assign directions, for example, as follows: 121→2 , 131→3 , 323→2 , 434→3 . Then the path for for the first message will be 131→3 , and for the second one — 4324→3→2 .

In the third sample test you can assign directions, for example, as follows: 121→2 , 212→1 , 232→3 . Then the path for the first message will be 1231→2→3 , and for the second one — 212→1 .

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