#!/usr/bin/env gawk

# Challenge 119
#
# TASK #2 - Sequence without 1-on-1
# Submitted by: Cheok-Yin Fung
# Write a script to generate sequence starting at 1. Consider the increasing
# sequence of integers which contain only 1’s, 2’s and 3’s, and do not have any
# doublets of 1’s like below. Please accept a positive integer $N and print the
# $Nth term in the generated sequence.
#
# 1, 2, 3, 12, 13, 21, 22, 23, 31, 32, 33, 121, 122, 123, 131,
#
# Example
# Input: $N = 5
# Output: 13
#
# Input: $N = 10
# Output: 32
#
# Input: $N = 60
# Output: 2223

function next_seq() {
    while (1) {
        n++
        if (match(n, "^[123]+$") && !match(n, "11")) {
            return n;
        }
    }
}

BEGIN {
    n = 0
    num = ARGV[1]
    for (i = 1; i <= num; i++)
        n = next_seq();
    print n
    exit
}