Mathematical Conference

202 participants from three countries attended a mathematical conference: Israel, Greece, and Japan.
On the first day, every pair of participants from the same country shook hands. On the second day, every pair of participants
where one was Israeli and the other was not Israeli shook hands. On the third day, every pair of participants where one
was Israeli and the other was Greek shook hands. In total, 20200 handshakes occurred. How many
Israeli participants were at the conference?