PROGRAM MAIN
    IMPLICIT NONE
    INTEGER :: B(9), I

    READ *, B(:)
    DO I = 1, 9
        IF (B(I) /= I) THEN
            PRINT *, I
            EXIT
        END IF
    END DO
    IF (B(9) == 9) THEN
        PRINT *, 10
    END IF
END PROGRAM MAIN