#include <iostream>
#include <fstream>
using namespace std;
ifstream fin ("interclasare1.in");
ofstream fout ("interclasare1.out");
int v[100];
int main()
{
int i,j,x,a,b,y,CONT=-2,INT1,INT2;
fin>>INT1;
while(fin>>x);{
v[x]++;
if(CONT==INT1)
INT2=x;
CONT++;
}
v[INT1]=0;
v[INT2]=0;
for(i=1;i<=999;i++)
    if(v[i]!=0)
    fout<<i;
    return 0;
}