⊦ char ≠ char0 → pos(char, char0 ' + chars) = pos(char, chars) + 1
'9' ≠ '6' ⊦ 3 = pos('9', '7' ' + '8' ' + '9' ') + 1
Used terms: '7' ' + '8' ' + '9' ', '6', '9'