Go: package main

import "fmt"

func main() {
	var n, r int
	fmt.Scan(&n, &r)
	for n != 0 || r != 0 {
		arr := make([]int, n)
		for i := range arr {
			arr[i] = len(arr) - i
		}

		for i := 0; i < r; i++ {
			var p, c int
			fmt.Scan(&p, &c)
			mid, top, last := arr[:p-1], arr[p-1:p-1+c], arr[p-1+c:]
			arr = append(append(append([]int{}, top...), mid...), last...)
		}
		fmt.Println(arr[0])
		fmt.Scan(&n, &r)
	}
}

C++: #include <bits/stdc++.h>
#include <iterator>
using namespace std;

struct Fast {Fast(){std::cin.tie(0);ios::sync_with_stdio(false);}} fast;

/* cpp template {{{ */

/* short */
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define Fi first
#define Se second
#define ALL(v) begin(v), end(v)
#define RALL(v) (v).rbegin(), (v).rend()
#define X real()
#define Y imag()

/* REPmacro */
#define REPS(i, a, n) for (ll i = (a); i < (ll)(n); ++i)
#define rep(i, n) REPS(i, 0, n)
#define REP1(i,n) for (ll i = 1; i <= (ll)(n); ++i)
#define RREP(i, n) REPS(i, 1, n + 1)
#define DEPS(i, a, n) for (ll i = (a); i >= (ll)(n); --i)
#define DEP(i, n) DEPS(i, n, 0)
#define EACH(i, n) for (auto&& i : n)

/* debug */
#define debug(x) cerr << x << " " << "(L:" << __LINE__ << ")" << '\n';

/* alias */
using ll = long long;
using ull = unsigned long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using pii = pair<int, int>;
using D = double;
using P = complex<D>;
using vs = vector<string>;
template <typename T> using PQ = priority_queue<T>;
template <typename T> using minPQ = priority_queue<T, vector<T>, greater<T>>;

/* const */
const int INF = 1001001001;
const ll LINF = 1001001001001001001ll;
const int MOD = 1e9 + 7;
const D EPS = 1e-9;
const int dx[] = {0, 1, 0, -1, 1, -1, 1, -1}, dy[] = {1, 0, -1, 0, 1, -1, -1, 1};

/* func */
inline bool inside(int y, int x, int H, int W) {return y >= 0 && x >= 0 && y < H && x < W;}
inline int in() {int x; cin >> x; return x;}
inline ll IN() {ll x; cin >> x; return x;}
inline vs split(const string& t, char c) {vs v; stringstream s(t); string b; while(getline(s, b, c)) v.eb(b); return v;}
template <typename T> inline bool chmin(T& a, const T& b) {if (a > b) a = b; return a > b;}
template <typename T> inline bool chmax(T& a, const T& b) {if (a < b) a = b; return a < b;}
template <typename T, typename S> inline void print(const pair<T, S>& p) {cout << p.first << " " << p.second << endl;}
template <typename T> inline void print(const T& x) {cout << x << '\n';}
template <typename T, typename S> inline void print(const vector<pair<T, S>>& v) {for (auto&& p : v) print(p);}
template <typename T> inline void print(const vector<T>& v, string s = " ") {rep(i, v.size()) cout << v[i] << (i != (ll)v.size() - 1 ? s : "\n");}

signed main() 
{
  int n,r;
  while(cin>>n>>r&&n&&r)
  {
    vi card(n);
    rep(i,n) card[i]=i;
    rep(i,r)
    {
      int p,c; cin>>p>>c;
      rep(k,c)
      {
        rep(j,p-1)
        {
          if(p==1) continue;
          swap(card[n-p-k],card[n-1-j-k]);
        }
      }
    }
    print(card[n-1]+1);
  } 

  return 0;
}

C++: #include <iostream>
#include <vector>
using namespace std;

int main(){
     while(1){
	  int N,R;
	  cin>>N>>R;
	  if(N==0)break;
	  vector<int> cards;
	  for(int i=1;i<N+1;i++){
	       cards.push_back(i);
	  }
	  for(int i=0;i<R;i++){
	       int p,c;
	       cin>>p>>c;
	       vector<int>::iterator pos=cards.begin();
	       pos+=N-c-(p-1);
	       vector<int> temp;
	       temp.assign(cards.begin()+(N-p+1),cards.end());
	       cards.insert(pos,temp.begin(),temp.end());
	       cards.erase((cards.begin()+N),cards.end());
	  }
	  //for(int i=0;i<N;i++){
	  //     cout<<i<<":"<<cards[i]<<endl;
	  //}
	  cout<<cards.back()<<endl;
     }
}