include<stdio.h>

int main(){
int n, i, m;
int a[1010] = {0};
int temp = 0;

scanf("%d", &n);
for(i = 0; i < n; i++ ){
    scanf("%d", &m);
    if(a[m] == 0){  //已有数字，跳过此步
        a[m] = m;  //m赋值给a[m]中
        temp++;
    }
}
printf("%d\n", temp);

for(i = 1; i < 1001; i++){
    if(a[i] != 0)
        printf("%d ", a[i]);
}
return 0;

}