# fibonacci conjecture
from random import randint
def isPrime(n, k=5): # miller-rabin
if n < 2: return False
for p in [2,3,5,7,11,13,17,19,23,29]:
if n % p == 0: return n == p
s, d = 0, n-1
while d % 2 == 0:
s, d = s+1, d/2
for i in range(k):
x = pow(randint(2, n-1), d, n)
if x == 1 or x == n-1: continue
for r in range(1, s):
x = (x * x) % n
if x == 1: return False
if x == n-1: break
else: return False
return True
fminus2, fminus1, f, n = 0, 1, 1, 1
while not isPrime(f*f+41):
fminus2 = fminus1
fminus1 = f
f = fminus2 + fminus1
n = n + 1
print n