TASK DEFINITION: In this task you will be given a string that only contains single digit numbers spelled out. The input string will not contain spaces between the different numbers. Your task is to return the number that the string spells out. The string will spell out each digit of the number for example '1726' will be 'oneseventwosix' instead of 'one thousand seven hundred six'.
PROBLEM: sevenfivezerofivetwoonenineseventhreetwothree

SOLUTION: 75052197323

PROBLEM: fivesevenonetwofourfivefivenineseven

SOLUTION: 571245597

PROBLEM: zerotwofourtwoone

SOLUTION:
02421