#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
using namespace std;

int main()
{
  int n, r;
  while(cin >> n >> r, n || r){
    vector<int> pile(n,1);
    partial_sum( pile.begin(), pile.end(), pile.begin() );

    for(int i = 0; i < r; ++i){
      int p, c;
      cin >> p >> c;
      rotate(pile.rbegin(), pile.rbegin() + p - 1, pile.rbegin() + p + c - 1);
    }

    cout << pile.back() << endl;
  }
}