#
# 1129: Hanafuda Shuffle
#

### constants 

### main

loop do
    n, r = gets.split.map(&:to_i)
    break if (n | r) == 0
    
    cards = (1..n).to_a.reverse
    
    r.times do
        pn, cn = gets.split.map(&:to_i)
        pn -= 1
        cards0 = cards[pn, cn] + cards[0, pn] + cards[(pn + cn)...n]
        cards = cards0
    end
    
    puts cards.first
end