Write a function that gets a string number and a fret of a 6-string guitar in 'standard tuning' and return the corresponding note. For this challenge we use a 24 fret model.

The notes are:

C, C#/Db, D, D#/Eb, E, F, F#/Gb, G, G#/Ab, A, A#/Bb, B

Try not to use a 2 dimensional array. Look at the image on the bottom to see the note names on the guitar neck.

Examples

string_fret(2, 10) ➞ "A"

string_fret(0, 16) ➞ "Invalid input"

string_fret(2, 19) ➞ "F#/Gb"

string_fret(3, 0) ➞ "G"

Notes

• If the string or fret number isn't correct return "Invalid input".
• 24 frets on the guitar neck.