PAT-A1041

#include<stdio.h>
#include<string.h>
int kk[100010];
int main(){
int i, n, len, k1, ans=-1, ascall[100010]={0};
scanf("%d",&n);
for(i=0;i<n;i++){
	scanf("%d",&k1);
	kk[i]=k1;
	ascall[k1]++;
}
for(i=0;i<n;i++){
	if(ascall[kk[i]]==1){ans=kk[i];break;}
}
if(ans==-1)printf("None\n");
else printf("%d\n",ans);
return 0;
}