#include<cstdio>
#include<algorithm>
#include<cmath>
#include<cstdlib>
#include<iostream>
const int N=1e4+10;
using namespace std;
int n,x,y,i,fa[N],f[N];
int find(int x){return fa[x]==x?x:fa[x]=find(fa[x]);}
int main()
{
    freopen("bzoj1854.in","r",stdin);
    freopen("bzoj1854.out"
 
,"w",stdout);
        scanf("%d\n",&n);
        for (i=1;i<=10000;i++) fa[i]=i;
        for (i=1;i<=n;i++)
        {
            scanf("%d%d\n",&x,&y);
            x=find(x);
            y=find(y);
            if (x==y) f[x]=1;
            else
            {
                if (x>y) swap(x,y);
                fa[x]=y;
                f[x]=1
 
;
            }
        }
        for (i=1;i<=n+1;i++)
            if (!f[i])
            {
                printf("%d",i-1);
                return 0;
            }
    fclose(stdin);
    fclose(stdout);
}