can anyone explain me the answer of below code

Question

def func(x):
res = 0
for i in range(x):
res += i
return res

print(func(4))

Answer 1

for i in range(4)
i takes the values from 0 to 3.
0+1+2+3=6 so res will return value as 6

Answer 2

0 +1+2+3=6