Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"sort"
	"strconv"
)

var scanner = bufio.NewScanner(os.Stdin)

func nextString() string {
	scanner.Scan()
	return scanner.Text()
}

func nextInt() (int, error) {
	return strconv.Atoi(nextString())
}

func main() {
	scanner.Split(bufio.ScanWords)

	n, _ := nextInt()
	m, _ := nextInt()

	arr := make([][]int, m)
	for i := range arr {
		a, _ := nextInt()
		b, _ := nextInt()
		arr[i] = []int{a, b}
	}

	sort.Slice(arr, func(i, j int) bool { return arr[i][0] > arr[j][0] })
	//	fmt.Println(arr)

	nGot := 0
	spent := 0
	for i := range arr {
		a := arr[i][0]
		b := arr[i][1]
		if a >= n {
			nGot++
		} else if a+b >= n {
			spent += n - a
			nGot++
		}
		if nGot >= m-1 {
			break
		}
	}
	fmt.Println(spent)
}

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

int main()
{
	//合計時間

	int N, M;
	cin >> N >> M;
	int a;
	vector<int> A;
	int b=0;
	for (int i = 0; i < 2*M; i++) {
		cin >> a;
		if (a < N) {
			A.push_back(a);
			break;
		}
		b++;
		cin >> a;
	}
	int sum = 0;
	if (b < M - 1) {
		sort(A.begin(), A.end());
		reverse(A.begin(), A.end());
		for (int i = 0; i < M - 1 - b; i++) {
			sum += N - A[i];
		}
	}
	cout << sum << endl;

	/*
	int sum=0, n;
	for (int i = 0; i < 4; i++) {
		cin >> n;
		sum += n;
	}
	cout << sum / 60 << endl;
	cout << sum % 60 << endl;
	//平均点
	/*
	int P[5];
	int sum=0;
	for (int i = 0; i < 5; i++) {
		cin >> P[i];
		if (P[i] < 40) P[i] = 40;
		sum += P[i];
	}
	cout << sum / 5 << endl;
	*/
	//投票
	/*
	int N, M;
	cin >> N >> M;
	int A[1000], vote[1000];
	for (int i = 0; i < N; i++) {
		cin >> A[i];
		vote[i] = 0;
	}
	int b;
	for (int i = 0; i < M; i++) {
		cin >> b;
		for (int j = 0; j < N; j++) {
			if (A[j] <= b) {
				vote[j]++;
				break;
			}
		}
	}
	int temps = 0, ans;
	for (int i = 0; i < N; i++) {
		if (vote[i] > temps) {
			temps = vote[i];
			ans = i;
		}
	}
	cout << ans + 1 << endl;
	*/

	//2.すごろく	
	/*
	int n;
	cin >> n;
	int A, _A = 1;
	int k = 0;
	int A_count[100];
	A_count[0] = 1;
	for (int i = 0; i < n; i++)
	{
	cin >> A;
	if (A == 1)
	{
	if (A == _A)
	{
	A_count[k]++;
	}
	else
	{
	k++;
	A_count[k] = 2;
	}
	}
	_A = A;
	}
	sort(A_count, A_count + k + 1);
	cout << A_count[k] << endl;
	*/

	//タイムカード
	/*
	int t[2][3];
	int x[3][3];
	for (int n=0; n < 3; n++)
	{
	for (int i=0; i < 2; i++)
	for (int k=0; k < 3; k++)
	cin >> t[i][k];

	for (int m = 2; m >= 0; m--)
	{
	x[n][m] = t[1][m] - t[0][m];
	if (t[0][m] > t[1][m])
	{
	x[n][m] += 60;
	t[1][m - 1]--;
	}
	}
	}
	for (int n= 0; n < 3; n++)
	{
	cout << x[n][0] << ' ' << x[n][1] <<' '<< x[n][2] << endl;
	}
	*/



	return 0;
}

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

int main()
{
	//合計時間

	int N, M;
	cin >> N >> M;
	int a;
	int A[5000];
	int b = 0;
	int x = 0;
	for (int i = 0; i < 2 * M; i++) {
		cin >> a;
		if (a < N) {
			A[x]=a;
			x++;
		}
		else
		{
			b++;
		} 
		cin >> a;
	}
	int sum = 0;
	if (b < M - 1) {
		sort(A, A+x);
		reverse(A, A+x);
		for (int i = 0; i < M - 1 - b; i++) {
			sum += N - A[i];
		}
	}
	cout << sum << endl;

	/*
	int sum=0, n;
	for (int i = 0; i < 4; i++) {
	cin >> n;
	sum += n;
	}
	cout << sum / 60 << endl;
	cout << sum % 60 << endl;
	//平均点
	/*
	int P[5];
	int sum=0;
	for (int i = 0; i < 5; i++) {
	cin >> P[i];
	if (P[i] < 40) P[i] = 40;
	sum += P[i];
	}
	cout << sum / 5 << endl;
	*/
	//投票
	/*
	int N, M;
	cin >> N >> M;
	int A[1000], vote[1000];
	for (int i = 0; i < N; i++) {
	cin >> A[i];
	vote[i] = 0;
	}
	int b;
	for (int i = 0; i < M; i++) {
	cin >> b;
	for (int j = 0; j < N; j++) {
	if (A[j] <= b) {
	vote[j]++;
	break;
	}
	}
	}
	int temps = 0, ans;
	for (int i = 0; i < N; i++) {
	if (vote[i] > temps) {
	temps = vote[i];
	ans = i;
	}
	}
	cout << ans + 1 << endl;
	*/

	//2.すごろく	
	/*
	int n;
	cin >> n;
	int A, _A = 1;
	int k = 0;
	int A_count[100];
	A_count[0] = 1;
	for (int i = 0; i < n; i++)
	{
	cin >> A;
	if (A == 1)
	{
	if (A == _A)
	{
	A_count[k]++;
	}
	else
	{
	k++;
	A_count[k] = 2;
	}
	}
	_A = A;
	}
	sort(A_count, A_count + k + 1);
	cout << A_count[k] << endl;
	*/

	//タイムカード
	/*
	int t[2][3];
	int x[3][3];
	for (int n=0; n < 3; n++)
	{
	for (int i=0; i < 2; i++)
	for (int k=0; k < 3; k++)
	cin >> t[i][k];

	for (int m = 2; m >= 0; m--)
	{
	x[n][m] = t[1][m] - t[0][m];
	if (t[0][m] > t[1][m])
	{
	x[n][m] += 60;
	t[1][m - 1]--;
	}
	}
	}
	for (int n= 0; n < 3; n++)
	{
	cout << x[n][0] << ' ' << x[n][1] <<' '<< x[n][2] << endl;
	}
	*/



	return 0;
}

C++: #include<iostream>
#include<algorithm>
using namespace std;
int main(){
	int n, m;
	cin >> n >> m;
	int c[1010];
	for (int i = 0; i < m; i++){
		int a;
		cin >> c[i] >> a;
	}
	sort(c, c + m);
	int sum = 0;
	for (int i = 1; i < m; i++){
		sum += max(0, n - c[i]);
	}
	cout << sum << endl;
	char ch; cin >> ch;
}

C++: #include <stdio.h>
#include <cmath>
#include <algorithm>
#include <stack>
#include <queue>
#include <vector>

using namespace std;

struct Info{
	Info(){
		good = bad = -1;
	}
	int good,bad;
};

int main(){

	int N,M,count = 0,index = 0,sum = 0;

	scanf("%d %d",&N,&M);
	Info info[M];

	int left,right;

	for(int loop = 0; loop < M; loop++){
		scanf("%d %d",&left,&right);
		if(left >= N){
			count++;
		}else{
			info[index].good = left;
			info[index].bad = right;
			index++;
		}
	}

	if(count < M-1){
		for(int i = 1; i <= index-1; i++){
			for(int k = index-1; k >= i; k--){
				if(info[k].good > info[k-1].good)swap(info[k],info[k-1]);
			}
		}

		for(int i = 0; i < index; i++){
			sum += (N-info[i].good);
			count++;
			if(count == M-1)break;
		}
	}

	printf("%d\n",sum);

	return 0;
}

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

int main(){
        int n, m, gbg;
        scanf("%d %d", &n, &m);
        int hit[m];
        for(int i=0; i<m; i++) scanf("%d %d", &hit[i], &gbg);
        sort(hit, hit+m);

        int ans=0;
        for(int i=m-1; i>0; i--) ans += max(0, n-hit[i]);
        printf("%d\n", ans);
        return 0;
}

C++: #include <bits/stdc++.h>
#define rep(i,n)for(long long i=0;i<(n);i++)
using namespace std;
using P=pair<long long,long long>;
typedef unsigned long long ull;
typedef long long ll;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
 
const ll MOD=1e9+7;
const ll INF=1e18;
const double pi=acos(-1);
int dx[4]={1,0,-1,0};
int dy[4]={0,1,0,-1};


int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);  
  
  int n,m;
  cin >> n >> m;
  vector<int>vec(m);
  rep(i,m){
    int a,b;
    cin >> a >> b;
    vec[i]=n-a;
  }
  sort(vec.begin(),vec.end());
  int cnt=0;
  int ans=0;
  rep(i,m){
    if(vec[i]<=0)cnt++;
    else{
      cnt++;
      ans+=vec[i];
    }
    if(cnt==m-1)break;
  }
  cout << ans << endl;
}

C++: #include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cmath>
#include <map>
#include <stack>
#include <queue>
#include <cstdio>
#include <cstdlib>
#include <utility>
using namespace std;
#define MAX 100005

int main(){
	int n, m, a[1005], t;
	cin >> n >> m;
	for(int i = 0;i < m;i++)cin >> a[i] >> t;
	sort(a, a+m);
	int ans = 0;
	for(int i = m-1;i > 0;i--){
		if(a[i] < n)ans += n-a[i];
	}
	cout << ans << endl;
	return 0;
}