#include <iostream>
#include <fstream>
using namespace std;

ifstream fin("bac.txt");
int main()
{
   int frecv[101]={0}, a, i, j = -1, ok, ok2;
   ok=ok2=0;
    while (fin >> a)
        frecv[a]++;
    for (i = 0; i <= 100; i++)
    {
        if (!(frecv[i]))
            ok++;
        else
        {
            if (ok >= 1 && j != -1)
            {
                cout << j << " " << i << '\n';
                ok2++;
                j = i;
                ok = 0;
            }
            else
            {
                j = i;
                ok = 0;
            }
        }
    }
    if (ok2 == 0)
        cout << "Nu exista";
    fin.close();
    return 0;
}