n = input()
n = int(n)
i = n
while i >= 2:
k = int(i**0.5)
c = 0
for j in range(2,k+1):
if i % j == 0 :
c += 1
break
if c == 0:
break
i -=1
print(i)
biA9IGlucHV0KCkKbiA9IGludChuKSAgICAgICAgCmkgPSBuCndoaWxlIGkgPj0gMjoKICAgIGsgPSBpbnQoaSoqMC41KQogICAgYyA9IDAKICAgIGZvciBqIGluIHJhbmdlKDIsaysxKToKICAgICAgICBpZiBpICUgaiA9PSAwIDoKICAgICAgICAgICAgYyArPSAxCiAgICAgICAgICAgIGJyZWFrCiAgICBpZiBjID09IDA6CiAgICAgICAgYnJlYWsgIAogICAgaSAtPTEKcHJpbnQoaSkKICAgICAg