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++: #define _USE_MATH_DEFINES
#include<iostream>
#include<string>
#include<cmath>
#include<queue>
#include<map>
#include<set>
#include<list>
#include<iomanip>
#include<vector>
#include<random>
#include<functional>
#include<algorithm>
#include<cstdio>
#include<unordered_map>
using namespace std;
//---------------------------------------------------
//ライブラリゾーン！！！！
typedef long long ll;
typedef long double ld;
#define str string
#define rep(i,j) for(ll i=0;i<(long long)(j);i++)
const ll Mod = 1000000007;
const ll gosenchou = 5000000000000000;
short gh[2][4] = { { 0,0,-1,1 },{ -1,1,0,0 } };
struct P {
	ll pos, cost;
};
bool operator<(P a, P b) { return a.cost < b.cost; }
bool operator>(P a, P b) { return a.cost > b.cost; }
struct B {//隣接リスト表現
	ll to;
	ld cost;
};
struct E {//辺の情報を入れる変数
	ll from, to, cost;
};
bool operator<(E a, E b) {
	return a.cost < b.cost;
}
struct H {
	ll x, y;
};
bool operator<(H a, H b) {
	/*if (a.x != b.x) return a.x < b.x;
	return a.y < b.y;*/
	return ((a.x + 1)*(a.y + 1)) < ((b.x + 1)*(b.y + 1));
}
bool operator>(H a, H b) {
	if (a.x != b.x) return a.x > b.x;
	return a.y > b.y;
}
bool operator==(H a, H b) {
	return a.x == b.x&&a.y == b.y;
}
bool operator!=(H a, H b) {
	return a.x != b.x || a.y != b.y;
}
ll gcm(ll i, ll j) {//最大公約数
	if (i > j) swap(i, j);
	if (i == 0) return j;
	return gcm(j%i, i);
}
ld rad(H a, H b) {
	return sqrt(pow(a.x - b.x, 2.0) + pow(a.y - b.y, 2.0));
}//rad＝座標上の2点間の距離
ll ari(ll a, ll b, ll c) {
	return (a + b)*c / 2;
}//等差数列の和
bool suf(ld a, ld b, ld c, ld d) {
	if (b <= c || d <= a) return 0;
	return 1;
}//[a,b),[c,d)
ll fact(ll x, ll k, ll p) {//最大値、個数
	ll sum = 1;
	for (int i = 0; i < k; i++) {
		sum *= (x--);
		sum %= p;
	}
	return sum;
}//階乗(正）
ll mod_pow(ll x, ll n, ll p) {
	ll res = 1;
	while (n > 0) {
		if (n & 1) res = res*x%p;
		x = x*x%p;
		n >>= 1;
	}
	return res;
}//x^n%p
 //#define int long long
const long long inf = 4523372036854775807;
const int iinf = 1500000000;
//----------------------------------------------------
//++++++++++++++++++++++++++++++++++++++++++++++++++++
int n;
H a[100000];
int b[100003];
signed main() {
	cin >> n;
	for (int i = 0; i < n; i++) {
		cin >> a[i].x >> a[i].y;
		b[a[i].x]++; b[a[i].y + 1]--;
	}
	for (int i = 1; i < 100003; i++) {
		b[i] += b[i - 1];
	}
	int ans = 0;
	for (int i = 0; i <= 100000; i++) {
		if (b[i + 1] >= i) ans = i;
	}
	cout << ans << endl;
	getchar(); getchar();
}

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

using namespace std;

int main(){

	int N,left,right,maximum;
	scanf("%d",&N);

	int* table = new int[100003];
	for(int i = 0; i <= 100002; i++){
		table[i] = 0;
	}

	for(int i = 0; i < N; i++){
		scanf("%d %d",&left,&right);
		table[left]++;
		table[right+1]--;
	}

	maximum = 0;
	for(int i = 1; i <= N+1; i++){
		table[i] += table[i-1];
		if(table[i] >= i){
			maximum = table[i];
		}
	}

	printf("%d\n",min(N-1,max(maximum-1,0)));

	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 <cstdio>
#include <queue>
#include <stack>
#include <vector>
#include <algorithm>
#include <string>
#include <cstring>
#include <cmath>
#include <complex>
#include <map>
#include <climits>
#include <sstream>
using namespace std;

#define reep(i,a,b) for(int i=(a);i<(b);++i)
#define rep(i,n) reep((i),0,(n))
#define ALL(v) (v).begin(),(v).end()
#define PB push_back
#define EPS 1e-8
#define F first
#define S second
#define mkp make_pair

static const double PI=6*asin(0.5);
typedef long long ll;
typedef complex<double> CP;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef vector<int> vint;
static const int INF=1<<24;

template <class T>
void initvv(vector<vector<T> > &v,int a,int b, const T  &t = T()){
	v.assign(a,vector<T>(b,t));
}

//v.erase(unique(v.begin(),v.end()),v.end());

#define MAX_SIZE 1000100
// int a[100010]={0};
ll all[MAX_SIZE - 1], part[MAX_SIZE - 1]; // segment tree
void add(int a,int b,int x,int k,int l,int r){
	if(a<=l&&r<=b){
		all[k]+=x;
	}
	else if(l<b&&a<r){
		part[k]+=(min(b,r)-max(a,l))*x;
		add(a,b,x,k*2+1,l,(l+r)/2);
		add(a,b,x,k*2+2,(l+r)/2,r);
	}
}

ll sum(int a,int b,int k,int l,int r){
	// if(k>100010) cout<<"hoge"<<endl;
	// cout<<k<<" "<<l<<" "<<r<<endl;
	if(r<=a||b<=l){
		return 0;
	}
	if(a<=l&&r<=b){
		return all[k]*(r-l)+part[k];
	}

	else{

		ll res;
		res=(min(b,r)-max(a,l))*all[k];
		res+=sum(a,b,k*2+1,l,(l+r)/2);
		res+=sum(a,b,k*2+2,(l+r)/2,r);
		return res;
	}
	return 0;
	// return getsum(a,b,k,l,(l+r)/2)+getsum(a,b,k,(l+r)/2,r));
}



int main(){
	int n;
	cin>>n;
	rep(i,n){
		int a,b;
		cin>>a>>b;
		// cout<<a<<" "<<b<<endl;
		add(a,b+1,1,0,0,100005);
		// cout<<sum(a,b,0,0,100005)<<endl;
	}
	// ll ans=0;
	// cout<<0<<endl;
	int ans=0;
	rep(i,100005){
		ll t=sum(i+1,i+2,0,0,100005);
		if(i<=(int)t){
			ans=max(ans,i);
		}
	}
	cout<<ans<<endl;
}