#include <iostream>
#include <list>

using namespace std;

int main(void)
{
	int n, r;
	while(cin >> n >> r) {
		if(n == 0 && r == 0) break;

		list<int> deck, temp;

		for(int i = 1; i <= n; i++) {
			deck.push_front(i);
		}

		for(int i = 0; i < r; i++) {
			int p, c;
			cin >> p >> c;

			list<int>::iterator p1, p2;
			p1 = deck.begin();
			while(--p > 0) { ++p1; }
			p2 = p1;
			while(c-- > 0) { ++p2; }

			temp.splice(temp.begin(), deck, p1, p2);
			deck.splice(deck.begin(), temp, temp.begin(), temp.end());
		}

		cout << deck.front() << endl;
	}

	return 0;
}