n = int(input("Nhap ban phim : "))

s = 0
for i in range(n):
    s += i 

print (s)
6acfdefc696d7dbc4cfb48c6c7e2bc75d67b44b9
<mask token>

<mask token>
for i in range(n):
    s += i
print(s)

n = int(input('Nhap ban phim : '))
s = 0
for i in range(n):
    s += i
print(s)

n = int(input("Nhap ban phim : "))

s = 0
for i in range(n):
    s += i 

print (s)