AOJ Volume11-1129

http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=1129&lang=jp

#define _USE_MATH_DEFINES
#include <iostream>
#include <vector>
#include <list>
#include <cmath>
#include <algorithm>
using namespace std;

int main ()
{
    int n,r;
    while (cin >> n >> r) {
        if (n == 0) {
            break;
        }
        
        
        list<int> w;
        for (int i=0; i < n; i++) {
            w.push_front(i+1);
        }
        
        for (int i=0; i < r; i++) {
            int p,c;
            cin >> p >> c;
            
            int tmp[c];
            list<int>::iterator it = w.begin();
            advance( it, (p - 1) );
            for (int j=0; j < c; j++) {
                tmp[j] = *it;
                *it = 0;
                it++;
            }
            w.remove(0);
            for (int j=c-1; j >= 0; j--) {
                w.push_front(tmp[j]);
            }
        }
        
        list<int>::iterator it = w.begin();
        cout << *it << endl;
        
    }
    
    
    return 0;
}