import math
import random

def countSumByCycle(start, stop):
    result = 0
    for i in range(start, stop + 1):
        result += i
    return result


def countSumByFormula(start, stop):
    n = stop - start + 1
    return (start + stop) * n / 2.0


print(countSumByCycle(50, 100))
print(countSumByFormula(50, 100))