Spit Problem

2000ms

262144K

Description:

In a Berland's zoo there is an enclosure with camels. It is known that camels like to spit. Bob watched these interesting animals for the whole day and registered in his notepad where each animal spitted. Now he wants to know if in the zoo there are two camels, which spitted at each other. Help him to solve this task.

The trajectory of a camel's spit is an arc, i.e. if the camel in position x spits d meters right, he can hit only the camel in position x + d, if such a camel exists.

Input:

The first line contains integer n (1 ≤ n ≤ 100) — the amount of camels in the zoo. Each of the following n lines contains two integers x_i and d_i ( - 10⁴ ≤ x_i ≤ 10⁴, 1 ≤ |d_i| ≤ 2·10⁴) — records in Bob's notepad. x_i is a position of the i-th camel, and d_i is a distance at which the i-th camel spitted. Positive values of d_i correspond to the spits right, negative values correspond to the spits left. No two camels may stand in the same position.

Output:

If there are two camels, which spitted at each other, output YES. Otherwise, output NO.

Sample Input:

2
0 1
1 -1

Sample Output:

YES

Sample Input:

Sample Output:

NO

Sample Input:

Sample Output:

YES

Informação

Provedor Codeforces

Código CF29A