B - Iroha Loves Strings (ABC Edition).cpp

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;

int main()
{
    int n, l;
    cin >> n >> l;
    vector<string>s(n);
    for (int i = 0; i < n; i++)
        cin >> s[i];
    sort(s.begin(), s.end());
    for (int i = 0; i < n; i++)
        cout << s[i];
    cout << endl;
    return 0;
}