3. Write a function that extract a number from a string. The string can contain any character. The number you return is the concatenation of all the digits you find in the string. For example, the extracted number from the string "sk8dfjn*HG23Yh$%7-5~5" is 823755. Test your function with the following: "1ksdj4sdf>R?387BDYGrrf%44@2"