#include<iostream> #include<cstdio> #include<cstring> #include<cmath> #include<iomanip> # include<stdio.h> using namespace std; int main() { int n,s; cin>>n; int a[1000] = {0}; for(int i=1;i<=n;i++){ cin>>s; a[s]++; } for(int i=1;i<=100;i++){ if(a[i]==1){ cout<<i; } } }