str = eval(input())

x = int(str)



res = 1

s = 0

for i in range(1, 10 ** 5):

  s = s + i

  if s >= x:

    res = i

    break



print(res)



import math



str = eval(input())

x = int(str)



res = math.ceil((-1 + math.sqrt(1 + 8 * x)) / 2.0)



print(res)

str = eval(input())
x = int(str)
res = 1
s = 0
for i in range(1, 10**5):
    s = s + i
    if s >= x:
        res = i
        break
print(res)

import math

str = eval(input())
x = int(str)
res = math.ceil((-1 + math.sqrt(1 + 8 * x)) / 2.0)
print(res)

+import math + -res = 1 -s = 0 -for i in range(1, 10**5): -    s = s + i -    if s >= x: -        res = i -        break +res = math.ceil((-1 + math.sqrt(1 + 8 * x)) / 2.0)