# Failure Is a Good Thing

Time Limit: 2000/1000 MS (Java/Others)

Memory Limit: 32768/32768 K (Java/Others)

## Description

Last week, my granddaughter started kindergarten, and, as is conventional, I wished her success. I was lying. What I actually wish for her is failure. I believe in the power of failure.

Success is boring. Success is proving that you can do something that you already know you can do, or doing something correctly the first time, which can often be a problematical victory. First-time success is usually afluke. First-time failure, by contrast, is expected; it is the natural order of things.

Failure is how we learn. I have been told of an African phrase describing a good cook as "she who has broken many pots." If you've spent enough time in the kitchen to have broken a lot of pots, probably you know a fair amount about cooking. I once had a late dinner with a group of chefs, and they spent time comparing knife wounds and burn scars. They knew how much credibility their failures gave them.

-- "Failure Is a Good Thing"

There are many kinds of failure, one of them is failing in exams. An exam has finished, and the score of each students has also been calculated. It is known that different students may get the same score.

Before the teacher telling his/her students their score, All the students are very nervous, so they get together to guess the rank of themselves in this example and the rank count backwards. Now the problem is: how many of the guesses will be correct at most?

There are n (1 ≤ n ≤ 1000) students participate in the exam, and the i-th student guesses: his/her rank is r_{i} and is b_{i} count backwards. (1 ≤ r_{i}, b_{i} ≤ n), different students may guess the same. A student's rank is r means that there are r-1 students's score is higher than him/her and the concept is similar when counts backwards.

## Output

For each test case, output the answer.

## Source

2010 ACM-ICPC Multi-University Training Con