def sum_to_n(n: int):
"""sum_to_n is a function that sums numbers from 1 to n.
>>> sum_to_n(30)
465
>>> sum_to_n(100)
5050
>>> sum_to_n(5)
15
>>> sum_to_n(10)
55
>>> sum_to_n(1)
1
"""
return n * (n + 1) // 2