proc to_roman {i} {
    set map {1000 M 900 CM 500 D 400 CD 100 C 90 XC 50 L 40 XL 10 X 9 IX 5 V 4 IV 1 I}
    foreach {value roman} $map {
        while {$i >= $value} {
            append res $roman
            incr i -$value
        }
    }
    return $res
}