arr=[]
ta=[]
while true do
  n, r = gets.split.map(&:to_i)
  if n == 0 && r == 0
    break
  end
  arr = (1..n).to_a.reverse
  r.times do
        p, c = gets.split.map(&:to_i)
        p -= 1
        ta = arr[p...p+c] + arr[0...p] + arr[p+c..n]
        arr = ta
  end
  puts arr[0]
end

