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<cstdio>
#include<algorithm>
#include<vector>


using namespace std;

int main(void){


    int n,r;
    while(scanf("%d %d", &r, &n), n){
        int p,c;
        int x[128], y[128];
        for(int i = 0; i < r; i++){
            y[i] = r-i;
        }

        for(int i = 0; i < n; i++){
            int cnt = 0;
            for(int j = 0; j < r; j++)x[j] = y[j];


            scanf("%d %d", &p, &c);

            for(int j = p-1; j < p+c-1; j++){
                y[cnt] = x[j];
                cnt++;
                x[j] = -1;
            }

            for(int j = 0; j < r; j++)if(x[j] != -1){y[cnt] = x[j];cnt++;}
//            for(int j = 0; j < r ; j++)printf("%2d:%2d\n", x[j], y[j]);
        }

        for(int j = 0; j < r; j++)x[j] = y[j];
        printf("%d\n", x[0]);
    }
    return 0;
}

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

void show_v( vector<int> v ){
    for(vector<int>::iterator it=v.begin(); it!=v.end(); it++){
        cout << *it << ' ';
    }
    cout << endl;
}

int main(){
    int n, r, i, j, p, c;
    while( cin >> n >> r, n||r ){
        vector<int> card(n);
        for(i = 0; i < n; i++){
            card[i] = n-i;
        }
        while( r-- > 0 ){
            cin >> p >> c;
            vector<int> tmp;
            tmp.assign( card.begin()+p-1, card.begin()+p+c-1 );
            card.erase( card.begin()+p-1, card.begin()+p+c-1 );
            tmp.insert( tmp.end(), card.begin(), card.end() );
            card.assign( tmp.begin(), tmp.end() );
        }
        cout << card[0] << endl;
    }
    return 0;
}

C++: #include<iostream>

using namespace std;

int main(){

   while(1){

      int n, r;
      cin>> n>> r;
      if(n==0&&r==0) break;
      int a[n];
      for(int i=0; i<n; i++) a[i]=n-i;
      for(int i=0; i<r; i++){
         int p, c;
         cin>> p>> c;
         int b[c];
         for(int j=p-1; j<p+c-1; j++){
            b[j-(p-1)]=a[j];
         }
         for(int j=p+c-2; j>c-1; j--){
            a[j]=a[j-c];
         }
         for(int j=0; j<c; j++){
            a[j]=b[j];
         }
      }

      cout<< a[0]<< endl;
   }
   return 0;
}

C++: #include <iostream>
#include <vector>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <algorithm>
#include <math.h>
#include <string>
#include <climits>
#include <assert.h>
#include <iomanip>
#include <bitset>

#define FOR(i,a,b) for(int i= (a); i<((int)b); ++i)
#define FOE(i,a) for(auto i : a)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define SUM(x) std::accumulate(ALL(x), 0LL)
#define MIN(v) *std::min_element(v.begin(), v.end())
#define MAX(v) *std::max_element(v.begin(), v.end())
#define EXIST(v,x) (std::find(v.begin(), v.end(), x) != v.end())
#define IS_BIT_ON(bit, i) (bit & (1 << i))
#define BIT_ON(bit, i) (bit |= (1 << i))
#define BIT_OFF(bit, i) (bit &= ~(1 << i))
#define BIT_COUNT(bit) (__builtin_popcount(bit))

typedef long long LL;
template<typename T> std::vector<T> make_v(size_t a){return std::vector<T>(a);}
template<typename T,typename... Ts> auto make_v(size_t a, Ts... ts){ return std::vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...));}    // C++14
template<typename T,typename V> typename std::enable_if<std::is_class<T>::value==0>::type fill_v(T &t,const V &v){t=v;}
template<typename T,typename V> typename std::enable_if<std::is_class<T>::value!=0>::type fill_v(T &t,const V &v){for(auto &e:t) fill_v(e,v);}
template<class T> inline T ceil(T a, T b) { return (a + b - 1) / b; }
void print() { std::cout << std::endl; }
template <class Head, class... Tail> void print(Head&& head, Tail&&... tail) { std::cout << head; if (sizeof...(tail) != 0) {std::cout << " ";} print(std::forward<Tail>(tail)...); }
template <class T> void print(std::vector<T> &v) {for (auto& a : v) { std::cout << a; if (&a != &v.back()) {std::cout << " ";} }std::cout << std::endl;}
template <class T> void print(std::vector<std::vector<T>> &vv) { for (auto& v : vv) { print(v); }}
inline bool inside(long long y, long long x, long long H, long long W) {return 0 <= y and y < H and 0 <= x and x < W; }
template<class T> inline double euclidean_distance(T y1, T x1, T y2, T x2) { return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)); }
template<class T> inline double manhattan_distance(T y1, T x1, T y2, T x2) { return abs(x1 - x2) + abs(y1 - y2); }
template<typename T> T &chmin(T &a, const T &b) { return a = std::min(a, b); }
template<typename T> T &chmax(T &a, const T &b) { return a = std::max(a, b); }

template<class T> inline std::vector<T> unique(std::vector<T> v) {
    sort(v.begin(), v.end());
    v.erase(unique(v.begin(), v.end()), v.end());
    return v;
}
// 初項s, 交差dのn個の数列の和
long long sum_of_arithmetic_progression(long long s, long long d, long long n) {
    return n * (2 * s + (n - 1) * d) / 2;
}

// 2のべき乗数かどうか
bool is_power_of_two(long long x) {
    return !(x & (x - 1));
}

// aとbの最大公約数 O(log min(a, b))
long long gcd(long long a, long long b) {
    if (b == 0) { return a; }
    return gcd(b, a % b);
}

// 数列vの最大公約数 O(N log d)
long long gcd(std::vector<long long> &v) {
    long long ans = v[0];
    for (int i = 1; i < (int)v.size(); ++i) {
        ans = gcd(ans, v[i]);
    }
    return ans;
}

// aとbの最小公倍数 O(log min(a, b))
long long lcm(long long a, long long b) {
    long long g = gcd(a, b);
    return a / g * b;
}

const int INF = 1u << 30u;
const long long LINF = 1ull << 58u;
const double EPS = 1e-9;
const long double PI = acos(-1.0);
const std::vector<int> dy2 = {0, 1}, dx2 = {1, 0};  // 右，下
const std::vector<int> dy4 = {0, 1, 0, -1}, dx4 = {1, 0, -1, 0};    // 右，下，左，上
const std::vector<int> dy8 = { 0, -1, 0, 1, 1, -1, -1, 1 }, dx8 = { 1, 0, -1, 0, 1, 1, -1, -1 };

using namespace std;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    while (true) {
        LL N, R;
        cin >> N >> R;

        if (N == 0 and R == 0) {
            return 0;
        }

        auto now = make_v<int>(N);
        FOR(i, 0, N) {
            now[i] = N - i;
        }

        FOR(_, 0, R) {
            LL P, C;
            cin >> P >> C;
            P--;

            auto next = make_v<int>(0);
            FOR(i, P, P + C) {
                next.emplace_back(now[i]);
            }
            FOR(i, 0, P) {
                next.emplace_back(now[i]);
            }
            FOR(i, P + C, N) {
                next.emplace_back(now[i]);
            }

            now = next;
        }

        print(now[0]);
    }

    return 0;
}

C++: #include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < n; ++i)
using ll = long long;
using namespace std;
const int INF = 1e9;

int main() {
    while (1) {
        int N, R;
        cin >> N >> R;
        if (N == 0 && R == 0)
            break;
        vector<int> A(N);
        rep(i, N) A[i] = N - i;

        rep(i, R) {
            int p, c;
            cin >> p >> c;
            --p;
            vector<int> utmp(p), dtmp(c);
            rep(i, p) utmp[i] = A[i];
            for (int i = p; i < p + c; ++i)
                dtmp[i - p] = A[i];

            rep(i, c) A[i] = dtmp[i];
            for (int i = c; i < c + p; ++i)
                A[i] = utmp[i - c];
        }
        cout << A[0] << "\n";
    }

    return 0;
}