Go: // A Way to Invite Friends(友だちの誘い方)
// http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=2331&lang=ja
package main

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

const N_MAX = 1000001

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)

	n := nextInt(sc)
	allow_list := make([]int, N_MAX+100)
	nMax := 0

	for i := 0; i < n; i++ {
		a, b := nextInt(sc), nextInt(sc)
		allow_list[a] += 1
		allow_list[b+1] += -1
		nMax = int(math.Max(float64(nMax), float64(b)))
	}

	for i := 2; i <= N_MAX; i++ {
		allow_list[i] += allow_list[i-1]
	}

	res := 0
	for i := 2; i <= nMax; i++ {
		if i-1 <= allow_list[i] { // i人誘う時に行きたい人の人数を超えないか(自分を含めて)
			res = i - 1 // 自分は除く
		}
	}

	fmt.Println(res)
}

func nextInt(sc *bufio.Scanner) int {
	sc.Scan()
	i, err := strconv.Atoi(sc.Text())
	if err != nil {
		panic(err)
	}
	return i
}

C++: #include <bits/stdc++.h>

#define FOR(i,a,b) for(int i= (a); i<((int)b); ++i)
#define RFOR(i,a) for(int i=(a); i >= 0; --i)
#define FOE(i,a) for(auto i : a)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define DUMP(x)  cerr << #x << " = " << (x) << endl;
#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 BIT(n) (1LL<<(n))
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end());

typedef long long LL;
template<typename T> using V = std::vector<T>;
template<typename T> using VV = std::vector<std::vector<T>>;
template<typename T> using VVV = std::vector<std::vector<std::vector<T>>>;

template<class T> inline T ceil(T a, T b) { return (a + b - 1) / b; }
template<class T> inline void print(T x) { std::cout << x << std::endl; }
template<class T> inline void print_vec(const std::vector<T> &v) { for (int i = 0; i < v.size(); ++i) {  if (i != 0) {std::cout << " ";} std::cout << v[i];} std::cout << "\n"; }
template<class T> inline bool inside(T y, T x, T H, T 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); }

const int INF = 1L << 30;
const double EPS = 1e-9;
const std::string YES = "YES", Yes = "Yes", NO = "NO", No = "No";
const std::vector<int> dy4 = { 0, 1, 0, -1 }, dx4 = { 1, 0, -1, 0 };    // 4近傍（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);

	int N;
	cin >> N;

	vector<int> dp(100100, 0);
	FOR(i, 0, N) {
	    int a, b;
	    cin >> a >> b;
	    dp[a] += 1;
	    dp[b + 1] -= 1;
	}

	FOR(i, 0, dp.size() - 1) {
	    dp[i + 1] += dp[i];
	}

	int ans = 0;
	FOR(i, 0, dp.size()) {
	    if (dp[i] >= i) {
            ans = max(ans, i - 1);
        }
	}
	print(ans);

	return 0;
}

C++: #include <iostream>
#include <string>
#include <queue>
#include <stack>
#include <algorithm>
#include <list>
#include <vector>
#include <complex>
#include <utility>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
#include <bitset>
#include <ctime>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <cassert>
#include <cstddef>
#include <iomanip>
#include <numeric>
#include <tuple>
#include <sstream>
#include <fstream>

using namespace std;
#define REP(i, n) for (int (i) = 0; (i) < (n); (i)++)
#define FOR(i, a, b) for (int (i) = (a); (i) < (b); (i)++)
#define RREP(i, a) for(int (i) = (a) - 1; (i) >= 0; (i)--)
#define FORR(i, a, b) for(int (i) = (a) - 1; (i) >= (b); (i)--)
#define DEBUG(C) cerr << #C << " = " << C << endl;
using LL = long long;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<LL>;
using VVL = vector<VL>;
using VD = vector<double>;
using VVD = vector<VD>;
using PII = pair<int, int>;
using PDD = pair<double, double>;
using PLL = pair<LL, LL>;
using VPII = vector<PII>;
template<typename T> using VT = vector<T>;
#define ALL(a) begin((a)), end((a))
#define RALL(a) rbegin((a)), rend((a))
#define SORT(a) sort(ALL((a)))
#define RSORT(a) sort(RALL((a)))
#define REVERSE(a) reverse(ALL((a)))
#define MP make_pair
#define FORE(a, b) for (auto &&a : (b))
#define FIND(s, e) ((s).find(e) != (s).end())
#define EB emplace_back

const int INF = 1e9;
const int MOD = INF + 7;
const LL LLINF = 1e18;

void solve(int N) {
    VI seg(100010, 0);
    REP(i, N) {
        int a, b;
        scanf("%d%d", &a, &b);
        seg[a]++;
        seg[b + 1]--;
    }
    REP(i, 100008) seg[i + 1] += seg[i];
    int ans = 0;
    FOR(i, 1, N + 1) {
        //cout << seg[i] << " ";
        if (seg[i] == i) ans = i;
    } 
    cout << (ans ? ans - 1 : 0) << endl;
    return;
}

signed main(void) {
    LL n, m, p, a, b, c, x, y, z, q;
    string s;
    bool f = false;
    while (cin >> n, n) {
        solve(n);
        return 0;
    }
}

C++: #include <iostream>
#include <string>
#include <utility>
#include <stack>
#include <vector>
#include <queue>
#include <algorithm>
#include <map>
#include <climits>
#include <set>
#include <numeric>
#include <iomanip>
#include <cmath>
#include <cstring>
using namespace std;
int cumsum[100002];
int main(){
  int N;
  cin >> N;
  for(int i = 0; i < N; i++){
    int a;
    int b;
    cin >> a >> b;
    cumsum[a] ++;
    if(b < N + 1){
      cumsum[b + 1] --;
    }
  }

  for(int i = 1; i <= N + 1; i++){
    cumsum[i] += cumsum[i - 1];
  }

  int ans = 0;
  for(int i = 0; i <= N + 1; i++){
    if(cumsum[i] + 1 >= i){
      ans = i - 1;
    }
  }
  cout << ans << endl;
  return 0;
}

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

int main(void){
    int n;
    cin >> n;
    int a[101010] = {};
    int l, r;
    for (int i = 0; i < n; i++) {
        cin >> l >> r;
        a[l]++;
        a[r+1]--;
    }
    for (int i = 0; i < n; i++) a[i+1] += a[i];
    
    int ans = 0;
    for (int i = 2; i < n+1; i++) {
        if (a[i]+1 >= i) {
            ans = max(ans, i);
        }
    }
    ans--;
    cout << ans << endl;
}

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

typedef long long ll;
typedef unsigned long long ull;
typedef unsigned __int128 HASH;
typedef pair<int,int> pii;
typedef pair<ll, ll> pll;
typedef pair<ull, ull> pullull;
typedef pair<ll,int> plli;
typedef pair<double, int> pdbi;
typedef pair<int,pii> pipii;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<pii> vpii;
typedef vector<vector<int>> mat;

#define rep(i,n) for (int i=0;i<(n);i++)
#define rep2(i,a,b) for (int i=(a);i<(b);i++)
#define rrep(i,n) for (int i=(n);i>0;i--)
#define rrep2(i,a,b) for (int i=(a);i>b;i--)
#define pb push_back
#define fi first
#define se second
#define all(a) (a).begin(),(a).end()
#define rall(a) (a).rbegin(),(a).rend()

const ll hmod1 = 999999937;
const ll hmod2 = 1000000000 + 9;
const ll INF = 1<<30;
const ll mod = 10000 + 7;
const int dx4[4] = {1, 0, -1, 0};
const int dy4[4] = {0, 1, 0, -1};
const int dx8[8] = {1, 1, 1, 0, 0, -1, -1, -1};
const int dy8[8] = {0, 1, -1, 1, -1, 0, 1, -1};
const double pi = 3.141592653589793;

//#define int long long
#define addm(X, Y) (X) = ((X) + ((Y) % mod) + mod) % mod

int n;
int a[100000 + 5], b[100000 + 5];
int imos[100000 + 5];

signed main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    cin >> n;
    rep(i, n) {
        cin >> a[i] >> b[i];
        imos[a[i]]++;
        imos[b[i] + 1]--;
    }
    rep(i, 100000 + 3) imos[i + 1] += imos[i];
    int ans = 0;
    rep2(i, 2, 100000 + 5) {
        if (i <= imos[i]) ans = i - 1;
        else if (i == imos[i] + 1) ans = imos[i];
    }
    cout << ans << endl;
}