#include <iostream>
#include <vector>
#include <algorithm>
#include <bits/stdc++.h> // Sử dụng thư viện bits/stdc++.h
 
int main() {
    int n;
    if (!(std::cin >> n)) return 0;
    std::vector<int> consumption(n);
    for (int i = 0; i < n; ++i) {
        std::cin >> consumption[i];
    }
 
    std::sort(consumption.begin(), consumption.end());
 
    auto last = std::unique(consumption.begin(), consumption.end());
    consumption.erase(last, consumption.end());
 
    std::cout << consumption.size() << std::endl;
 
    for (size_t i = 0; i < consumption.size(); ++i) {
        std::cout << consumption[i] << (i == consumption.size() - 1 ? "" : " ");
    }
    std::cout << std::endl;
 
    return 0;
}

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