大水题,不多说
#include <cstdio>
int main(){
int n;
scanf("%d",&n);
int number[n]={0};
int number_times[10010]={0};
for (int i=0;i<n;i++){
int num;
scanf("%d",&num);
number_times[num]++;
number[i] = num;
}
for (int i=0;i<n;i++){
if (number_times[number[i]]==1) {
printf("%d",number[i]);
return 0;
} else {
if (i==n-1) printf("None");
}
}
return 0;
}