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'.

fivefourseveneightseveneight
547878

threesixsixeightzerozerotwo
3668002

threefiveninefiveseven

35957