# Ces programmes sont sous licence CeCILL-B V1.

from math import *

e = 1E-5
a = 2
b = 4
m = (a + b) / 2
while b - a > e and abs(sin(m)) > e:
  if sin(a) * sin(m) <= 0:
    b = m
  else:
    a = m
  m = (a + b) / 2
print(m)