#include<cstdio> using namespace std; int vis[100005] = {0}; int num[100005] = {0}; int main() { int n,i; scanf("%d",&n); for(i = 0; i<n; ++i) { scanf("%d",(num+i)); vis[*(num+i)]++; } for(i = 0; i<n; ++i) if(vis[*(num+i)]==1) break; if(i==n) puts("None"); else printf("%d\n",*(num+i)); return 0; }