In the following 6-digit number:
283910
91 is the greatest sequence of 2 consecutive digits.
In the following 10-digit number:
1234567890
67890 is the greatest sequence of 5 consecutive digits.
Complete the solution so that it returns the greatest sequence of five consecutive digits found within the number given. The number will be passed in as a string of only digits. It should return a five digit integer. The number passed may be as large as 1000 digits.