#include <iostream>
using namespace std;

class Date {

private:
  int year;
  int month;
  int day;

public:
  Date(int, int, int);
  void set(int, int, int);
  void print();

void print()
{
  cout << day << "-" << month << "-" << year << endl;
}

};

int main()
{
   Date today(1,1,2017);

   cout << "This program was written on ";
   today.print(); 

   cout << "This program was modified on ";
   today.set(18,1,2017);
   today.print();

   return 0;
}

Date::Date(int d, int m, int y)
{
  if(d>0 && d<31) day = d;
  if(m>0 && m<13) month = m;
  if(y>0) year =y;
}

void Date::set(int d, int m, int y)
{
  if(d>0 && d<31) day = d;
  if(m>0 && m<13) month = m;
  if(y>0) year =y;
}