text: #include <iostream>
  #include <cstdio>
  #include <vector>
  
  using namespace std;
  
  int main()
  {
      int test,num,out,j,k;
      scanf("%lld",&test);
      out=0;
      while(test--)
      {
          scanf("%d",&num);
          out=out^num;
      }
      cout<<out<<endl;
      return 0;
  }
  