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.

Contraintes

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

Exemples

Entrée :
people = 4

Sortie attendue :
expected = 6

Entrée :
long long people = 4;

Sortie attendue :
long long expected = 6;

Entrée :
long people = 4;

Sortie attendue :
long expected = 6;

Entrée :
people = 1

Sortie attendue :
expected = 0

Entrée :
long long people = 1;

Sortie attendue :
long long expected = 0;

Entrée :
long people = 1;

Sortie attendue :
long expected = 0;

Références

Ce défi a été adapté pour CodeUtility. Suivez l'énoncé et les contraintes ci-dessus.

• #26 Handshakes