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)

// by adiforluls
#pragma GCC optimize ("-O2")
#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#define FAST            ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0)
#define ll              long long
#define ld              long double
#define pb              push_back
#define mp              make_pair
#define pii             pair<int,int>
#define all(a)          (a).begin(),(a).end()
#define clz(a)          __builtin_clz(a) // count leading zeroes
#define ctz(a)          __builtin_ctz(a) // count trailing zeroes
#define popc(a)         __builtin_popcount(a) // count set bits (for ints only diff for ll)
#define rep(i,a,b)      for(int i=a;i<b;i++)
#define rfor(i,a,b)     for(int i=a; i>=b; i--)
#define debug(x)        cerr << #x << " = " << x << endl;
#define F               first
#define S               second
#define endl            '\n'
#define SIZE            1000005
#define deci(n)         cout<<fixed<<setprecision(n)
#define ordered_set     tree<pll, null_type,less<pll>, rb_tree_tag,tree_order_statistics_node_update>
// order_of_key(k)
// find_by_order(k)
const ld PI = acos(-1.0);
const int INF = 0x3f3f3f3f;
const ll lul2 = 998244353;
const ll lul = 1000000007;

void mod(ll &x)
{
    if(x>=lul) x-=lul;
    if(x<0) x+=lul;
}

ll _gcd(ll a, ll b)
{
    if(b == 0) return a;
    return _gcd(b,a%b);
}

ll expo(ll n, ll p)
{
    if(p == 0) return 1;
    ll x = expo((n*n)%lul, p/2)%lul;
    if(p&1) return (x*n)%lul;
    return x;
}
//---------------------------------------------------------------------

void solve()
{
    ll k; cin>>k;
    queue<string> q;
    string ans = "";
    for(char i='1'; i<='9'; i++)
    {
        string x = "";
        x+=i;
        q.push(x);
    }
    while(k)
    {
        ans = q.front();
        q.pop();
        for(char i = '0'; i<='9'; i++)
        {
            if(abs(ans.back()-i)<=1) q.push(ans+i);
        }
        k--;
    }
    cout<<ans;
}
int main()
{   
    FAST;
   //  #ifndef ONLINE_JUDGE
     // freopen("input.txt", "r", stdin);
     // freopen("output.txt", "w", stdout);
   //  #endif
    int t; t=1;
    rep(i,1,t+1){
        solve();
    }
    return 0;
}