HFIR2ILB6446RYDKLQUTGBMPCAXQQW54TX6MAQU7TA3FHH7XEC6AC
7PZ4CQFVYUMSJKVCNM75VKK5JCUYU6ICHWPZXXIC3S63YJVFCP5QC
BBLXANWIGYIXRFFG3OWZGDGYNGKBGESCU5RBGPCMYYKTPCNVCGYAC
LXTTOB33N2HCUZFIUDRQGGBVHK2HODRG4NBLH6RXRQZDCHF27BSAC
if #pat == 0 then return #s end
check_eq(rfind('abc', ''), 3, 'empty pattern')