Project Euler: #8 - Largest product in a series

Problem The four adjacent digits in the 1000-digit number that has the greatest product is 9 × 9 × 8 × 9 = 5832. 73167176531330624919225119674426574742355349194934969835203127745063262395783180169848018694788518438586156078911294949545950173795833195...