h_2

#include <bits/stdc++.h>
using namespace std;
int n,nr,res;
unordered_map<int,int> m;

int main()
{
    cin>>n;
    for(int i=0;i<n;++i)
        cin>>nr,++m[nr];
    res=INT_MAX;
    for(auto it=m.begin();it!=m.end();++it)
        if(it->second==1)
           res=min(res,it->first);
    cout<<res;
    return 0;
}