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.

Restrições

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

Exemplos

Entrada:
people = 4

Saída esperada:
expected = 6

Entrada:
long long people = 4;

Saída esperada:
long long expected = 6;

Entrada:
long people = 4;

Saída esperada:
long expected = 6;

Entrada:
people = 1

Saída esperada:
expected = 0

Entrada:
long long people = 1;

Saída esperada:
long long expected = 0;

Entrada:
long people = 1;

Saída esperada:
long expected = 0;

Referências

Este desafio foi adaptado para o CodeUtility. Siga o enunciado e as restrições acima.

• #26 Handshakes