# Hanafuda Shuffle

# Hanafuda Shuffle

There are a number of ways to shuffle a deck of cards. Hanafuda shuffling for Japanese card game '**Hanafuda**' is one such example. The following is how to perform Hanafuda shuffling.

There is a deck of **n** cards. Starting from the **p**-th card from the top of the deck, **c** cards are pulled out and put on the top of the deck, as shown in Figure. This operation, called a cutting operation, is repeated.

Write a program that simulates Hanafuda shuffling and answers which card will be finally placed on the top of the deck.

Figure: Cutting operation

#### Input

Consists of multiple data sets. Each data set starts with a line containing two positive integers **n** (**1** ≤ **n** ≤ **50**) and **r** (**1** ≤ **r** ≤ **50**); **n** and **r** are the number of cards in the deck and the number of cutting operations, respectively.

There are **r** more lines in the data set, each of which represents a cutting operation. These cutting operations are performed in the listed order. Each line contains two positive integers **p** and **c** (**p** + **c** ≤ **n** + **1**). Starting from the **p**-th card from the top of the deck, **c** cards should be pulled out and put on the top.

The end of the input is indicated by a line which contains two zeros.

#### Output

For each input data set your program should write the number of the top card after the shuffle. Assume that at the beginning the cards are numbered from **1** to **n**, from the bottom to the top. Each number should be written in a separate line without any superfluous characters such as leading or following spaces.

5 2 3 1 3 1 10 3 1 10 10 1 8 3 0 0

4 4