unique

#include<iostream>
#include<cstdio>
#include<cmath>
#include<algorithm>
#include<cstring>

using namespace std;

int n, a[5211314], len;

int main() {
	
	cin >> n;
	for (int i = 1; i <= n; ++ i) {
		cin >> a[i];
	}
	sort(a + 1, a + 1 + n);
	len = unique(a + 1, a + 1 + n) - (a + 1);
	//len是去重后的数组长度
	cout << "len = " << len << endl;
	for (int i = 1; i <= len; ++ i) {
		cout << a[i] << " ";
	}
}