#include <iostream>
#include <algorithm>
#include <cstdio>
#include <string>

#define ll long long

using namespace std;

int B[11];

int main(){
  
  int x;
  for(int i=0;i<9;++i){
      cin>>x;
      B[x]=1;
  }
  for(int i=1;i<=10;++i)
     if(!B[i]) cout<<i<<endl;
  
   return 0;
}