#include<iostream>
#include<cstdio>
#include<cmath>
#include<queue>
#include<vector>
#include<string.h>
#include<cstring>
#include<algorithm>
#include<set>
#include<map>
#include<fstream>
#include<cstdlib>
#include<ctime>
#include<list>
#include<climits>
#include<bitset>
using namespace std;
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define fopen freopen("input.in", "r", stdin);freopen("output.in", "w", stdout);
#define left asfdasdasdfasdfsdfasfsdfasfdas1
#define tan asfdasdasdfasdfasfdfasfsdfasfdas
typedef long long ll;
typedef unsigned int un;
const int desll[4][2]={{0,1},{0,-1},{1,0},{-1,0}};
const ll mod=1e9+7;
const int maxn=2e6+7;
const int maxm=1e6+7;
const double eps=1e-4;
int m,n;
int ar[maxn];
pair<int,int> pa[maxn];
map<int,int> ma;
bool wa[maxn];
int f[maxn];
int fin(int x)
{return f[x]==x?x:f[x]=fin(f[x]);
}
int main()
{scanf("%d",&n);m=0;for(int i=0;i<n;i++)scanf("%d%d",&pa[i].first,&pa[i].second),ar[m++]=pa[i].first,ar[m++]=pa[i].second;sort(ar,ar+m);m=unique(ar,ar+m)-ar;for(int i=0;i<m;i++){ma[ar[i]]=i;}for(int i=0;i<m;i++)f[i]=i;memset(wa,0,sizeof(wa));int ans=0;for(int i=0;i<n;i++){int a=pa[i].first,b=pa[i].second;if(!wa[ma[a]]){wa[ma[a]]=1;ans=max(ans,a);f[ma[a]]=ma[b];continue;}int x=fin(ma[a]);int y=fin(ma[b]);//分别寻找a，b指向的时间if(wa[x] && wa[y]){printf("-1\n");return 0;}if(wa[x]==false && wa[y]==false){if(ar[x]<ar[y]){f[x]=y;//更新时间指向的状态wa[x]=1;ans=max(ans, ar[x]);}else{f[y]=x;//更新时间指向的状态wa[y]=1;ans=max(ans, ar[y]);}}else if(!wa[x]){wa[x]=1;ans=max(ans, ar[x]);}else{wa[y]=1;ans=max(ans, ar[y]);}f[ma[a]]=y;//更新时间指向的状态}printf("%d\n",ans);return 0;
}