C++ :

#include<bits/stdc++.h>
using namespace std;
int n,a=1,b=2,c=4,x,y;
int main()
{ 
//    freopen("1.in","r",stdin);
 //   freopen("1.out","w",stdout);
    cin>>n;
   for(int i=0;i<n;i++)
    {
       cin>>x>>y;	
       if(a==x) a=y;
       else if(a==y) a=x;
    }
    cout<<a;
    
    return 0;
}