XuatHienNhieuHonMotLan

#include <stdio.h>
#include <math.h>
const int MAX = 100;
int check (int number, int arr[], int start, int end){
    int i = start;
    for(i = start; i < end; ++i){
        if(number == arr[i]){
            return 1;
        }
    }
    return 0;
}
int main(){
    int length, i;
    scanf("%d", &length);
    int arr[MAX];
    int key = 0;
    for (i = 0; i<length; ++i){
        scanf("%d", &arr[i]);
    }
    for (i = 0; i<length; ++i){
        if(check(arr[i], arr, 0,i)==0){
            if(check(arr[i], arr, i+1, length)){
                ++key;
                printf("%d ", arr[i]);
            }
        }
    }
    if(key==0){
        printf("%d", 0);
    }
    return 0;
}