Explicit random number

I want to invite some students to do a questionnaire survey at school , For the objectivity of the experiment , He first generated... By computer N individual 1 To 1000 Random integer between （N≤100）, For the repeated numbers , Keep only one , Take out the rest of the same number , Different numbers correspond to different student numbers . And then sort the numbers from small to large , According to the order of arrangement to find students to do research . Please help Mingming finish “ duplicate removal ” And “ Sort ” The job of .

 Input yes 2 That's ok 
 The first 1 Behavior 1 A positive integer , Represents the number of generated random numbers ：N
 The first 2 Yes N Positive integers separated by spaces , For the resulting random number .

 The output is 2 That's ok , The first 1 Behavior 1 A positive integer M, The number of different random numbers . The first 2 Behavior M Positive integers separated by spaces , Different random numbers in order from small to large .

Input 10 20 40 321 67 40 20 89 301 407 15

Output 8 15 20 40 67 89 301 321 407

#include <cstdio>
#include <set>
#include <iostream>
using namespace std;
int main() {
	set<int> s;
	int n, x;
	scanf("%d", &n);
	while(n--) {
		scanf("%d", &x);
		s.insert(x);
	}
	printf("%d\n", s.size());
	set<int>::iterator it  = s.begin();
	while(it != s.end()) {
		printf("%d ", *it);
		it++;
	}
	return 0;
}