Answer 1

Where's your attempt?

Hint: sum of consecutive can be found easily using any loops or much better use mathematics formula to do it.

Answer 2

https://www.sololearn.com/Discuss/2726770/?ref=app

https://www.sololearn.com/Discuss/2726783/?ref=app

https://www.sololearn.com/Discuss/2726795/?ref=app

Answer 3

N = int(input())
count = N
x = range(1, N +1)
for i in x:
N = i + N
print(N - count)