import bisect

from math import sqrt

x = int(eval(input()))

a = [1]

s = 1

for i in range(2, 2*int(sqrt(x))):

    s += i

    a.append(s)



if x in a:

    print((a.index(x) + 1))

    exit()



print((bisect.bisect_right(a, x)+1))



from math import sqrt

x = int(eval(input()))



t = (-1+sqrt(8*x+1))/2

a = int(t)



if a == t:

    print(a)

else:

    print((a+1))



import bisect
from math import sqrt

x = int(eval(input()))
a = [1]
s = 1
for i in range(2, 2 * int(sqrt(x))):
    s += i
    a.append(s)
if x in a:
    print((a.index(x) + 1))
    exit()
print((bisect.bisect_right(a, x) + 1))

from math import sqrt

x = int(eval(input()))
t = (-1 + sqrt(8 * x + 1)) / 2
a = int(t)
if a == t:
    print(a)
else:
    print((a + 1))

-import bisect -a = [1] -s = 1 -for i in range(2, 2 * int(sqrt(x))): -    s += i -    a.append(s) -if x in a: -    print((a.index(x) + 1)) -    exit() -print((bisect.bisect_right(a, x) + 1)) +t = (-1 + sqrt(8 * x + 1)) / 2 +a = int(t) +if a == t: +    print(a) +else: +    print((a + 1))