1 #include <bits/stdc++.h>
 2 
 3 using namespace std;
 4 
 5 int n,x;
 6 map<int,int>mp;
 7 int main()
 8 {
 9     while(~scanf("%d",&x)){
10         mp[x]++;
11     }
12     for(auto i:mp){
13         if(i.second==1)printf("%d\n",i.first);
14     }
15     return 0;
16 }