Count Handshakes

Every person shakes hands once with every other person. A handshake between A and B is the same event as one between B and A. Nobody shakes their own hand.

Implement handshake_count(people).

Input

people: The number of people.

Output

Return the total number of distinct handshakes.

Ограничения

0 ≤ people ≤ 1,000,000,000. The answer fits a signed 64-bit integer.

Примеры

Ввод:
people = 4

Ожидаемый вывод:
expected = 6

Ввод:
long long people = 4;

Ожидаемый вывод:
long long expected = 6;

Ввод:
long people = 4;

Ожидаемый вывод:
long expected = 6;

Ввод:
people = 1

Ожидаемый вывод:
expected = 0

Ввод:
long long people = 1;

Ожидаемый вывод:
long long expected = 0;

Ввод:
long people = 1;

Ожидаемый вывод:
long expected = 0;

Ссылки

Это задание адаптировано для CodeUtility. Следуйте условию и ограничениям выше.

• #26 Handshakes