Problem:
Score : 400 points

Problem Statement

A positive integer X is said to be a lunlun number if and only if the following condition is satisfied:

In the base ten representation of X (without leading zeros), for every pair of two adjacent digits, the absolute difference of those digits is at most 1.

For example, 1234, 1, and 334 are lunlun numbers, while none of 31415, 119, or 13579 is.

You are given a positive integer K. Find the K-th smallest lunlun number.

Constraints

1 \leq K \leq 10^5

All values in input are integers.

Input

Input is given from Standard Input in the following format:

K

Output

Print the answer.

Sample Input 1

15

Sample Output 1

23

We will list the 15 smallest lunlun numbers in ascending order:

1,
2,
3,
4,
5,
6,
7,
8,
9,
10,
11,
12,
21,
22,
23.

Thus, the answer is 23.

Sample Input 2

1

Sample Output 2

1

Sample Input 3

13

Sample Output 3

21

Sample Input 4

100000

Sample Output 4

3234566667

Note that the answer may not fit into the 32-bit signed integer type.

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
#define DEBUG
#ifdef DEBUG
#define debug(...) __f(#__VA_ARGS__, __VA_ARGS__)
	template <typename Arg1>
	void __f(const char* name, Arg1&& arg1){
		cerr << name << " : " << arg1 << std::endl;
	}
	template <typename Arg1, typename... Args>
	void __f(const char* names, Arg1&& arg1, Args&&... args){
		const char* comma = strchr(names + 1, ','); cerr.write(names, comma - names) << " : " << arg1<<" | ";__f(comma+1, args...);
	}
#else
#define debug(...)
#endif
#define FOR(i,a,b) 	for(int i=a;i<b;++i)
#define RFOR(i,a,b) 	for(int i=a;i>=b;--i)
#define ln 		"\n"
#define mp make_pair
#define pb push_back
#define sz(a)	ll(a.size())
#define F first
#define S second
#define all(c)	c.begin(),c.end()
#define rall(c) c.rbegin(), c.rend()
#define trace(c,x) for(auto &x:c)
#define pii pair<ll,ll>
#define init(a, x) memset(a,x,sizeof(a))
typedef long long ll;
typedef long double ld;
typedef	priority_queue<pii,std::vector<pii>,greater<pii> > revpr;

typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> pbds;
// ordered_set X
//K-th smallest
//*X.find_by_order(k-1)
//NO OF ELEMENTS < A
//X.order_of_key(A)
const int L=1e6+7;
map<ll,ll> counter;
ll fastexpo(ll x,ll y,ll m)
{
	ll temp=1;
	while(y>0)
	{
		if(y&1)temp = ((temp%m)*(x%m))%m;
		x = ((x%m)*(x%m))%m;
		y>>=1;
	}return temp;
}
void fff()
{
	int k;
	cin >> k;
	set<ll>SET;
	FOR(i,1,10)SET.insert(i);
	if(k <= 9)
	{
		cout<<k<<ln;
		return;
	}	
	int co = 9;
	while(co <= k)
	{
		set<ll>aux;
		trace(SET,x)
		{
			if(x%10 >= 1)
			{
				aux.insert(x*10 + (x%10)-1);
			}
			aux.insert(x*10 + (x%10));
			if(x%10 < 9)
			{
				aux.insert(x*10 + (x%10)+1);
			}
		}
		SET.clear();
		trace(aux, x)
		{
			co++;
			SET.insert(x);
			if(co == k)
			{
				cout<<x<<ln;
				return;
			}
		}
	}

}
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);
	//int t;cin >> t;while(t--)
	fff();
	return 0;
}