The following youths participate at the international youth meeting:
- John from the USA, 14 years old
- Pierre from France, 13 years old
- Stefan from Germany, 15 years old
- Marten from the Netherlands, 11 years old
- Ding from China, 12 years old
- Alberto from Spain, 15 years old
John says: there are four teenagers among us. Marten responds: that is not correct.
How many teenagers are there? How did Marten count?