# PP1 Week 3 Contest 2

# Lazybones

Student Valera is a classic example of the idler. In classes, he almost did not go, and only appears at the end of the semester at the university and deliver "tails". His dream: to find a day when it will be possible to pass at once all the debts. He has a schedule of work for teachers, of whom know exactly what to and what day of the month, each teacher will be available daily. Help Valera write a program that is scheduled to determine whether Valera pass all debts in one day or not.

#### Input

The first line contains the number of test cases. Each test consists of a number **n** (**1** ≤ **n** ≤ **100**) of items that need to pass Valera. This is followed by **n** lines, each of which consists of two numbers **a** and **b** (**1** ≤ **a** ≤ **b** ≤ **31**), specify the interval of the regular teacher.

#### Output

For each test print in a separate line "**YES**" if it is possible to meet all the teachers at one day, or "**NO**", if this is impossible.

2 1 1 2 2 1 2 3 4

YES NO