Gao The Sequence

Time Limit: 2 Seconds
Memory Limit: 65536 KB

You are given a sequence of integers,* A1,A2,...,An*. And you are allowed a manipulation on the sequence to transform the origin sequence into another sequence * B1,B2,...,Bn*(Maybe the two sequences are same ). The manipulation is specified as the following three steps:

1.Select an integer *Ai* and choose an arbitrary positive integer *delta* as you like.

2.Select some integers *Aj* satisfying j < i, let's suppose the selected integers are *Ak1,Ak2,...,Akt* , then subtract an arbitrary positive integer *Di* from *Aki (1 ≤ i ≤ t)* as long as sum(*Di*) = *delta*.

3.Subtract *delta* from *Ai*.

The manipulation can be performed any times. Can you find a way to transform * A1,A2,...,An* to * B1,B2,...,Bn* ?

#### Input

The input consist of multiple cases. Cases are about 100 or so. For each case, the first line contains an integer *N(1 ≤ N ≤ 10000)* indicating the number of the sequence. Then followed by N lines,
ith line contains two integers *Ai* and *Bi* *(0 ≤ Bi ≤ Ai ≤ 4294967296)*.

#### Output

Output a single line per case. Print "YES" if there is a certain way to transform Sequence *A* into Sequence *B*. Print "NO" if not.

#### Sample Input

3
3 2
4 2
5 2
3
2 0
7 1
3 1

#### Sample Output

YES
NO

Author:

**LI, Wenchao**
Contest:

**ZOJ Monthly, November 2012**
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