REM Modular inverse
    LET E=42
    LET T=2017
    GOSUB 100
    PRINT M
    END

    REM Increments E S (step) times until B is greater than T
    REM Repeats until B = 1 (MOD = 1) and C (count)
    REM B will not be greater than T + E
100 LET D=0
    IF E>=T THEN GOTO 130
    LET B=E
    REM At least one iteration is necessary
    LET S=((T-B)/E)+1
    LET B=B+S*E
    LET C=1+S
    LET B=B-T
110 IF B=1 THEN GOTO 120
    LET S=((T-B)/E)+1
    LET B=B+S*E
    LET C=C+S
    LET B=B-T
    GOTO 110
120 LET D=C
130 LET M=D
    RETURN