## Task 3 - 150523

When a pioneer group reported on their trips taken over the past few years, the following was revealed:

(1) Exactly 13 members of this group have been to the Baltic Sea.

(2) Exactly 15 pioneers have been to the Harz.

(3) Exactly 6 pioneers have been to both the Baltic Sea and the Harz.

(4) Exactly 4 pioneers have never been to either the Baltic Sea or the Harz.

Determine the total number of pioneers who belong to this group!