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 (GCC 5.4.1) (judge verdict: Accepted)

#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#include<string.h>
#include<stdbool.h>
typedef long long ll;
typedef long double ld;
#define rep(i,l,r)for(ll i=(l);i<(r);i++)
#define repp(i,l,r,k)for(ll i=(l);i<(r);i+=(k))
#define rrep(i,l,r)for(ll i=(l);i>=(r);i--)
#define INF (1LL<<60)
#define MOD1 1000000007
#define MOD2 998244353
#define MAX_N (1 << 17)
#define YES printf("Yes\n")
#define NO printf("No\n")
#define PN printf("\n")

void swap(ll *a, ll *b){ll c;c=*b;*b=*a;*a=c;}
ll max2(ll a,ll b){return a>=b?a:b;}
ll min2(ll a,ll b){return a>=b?b:a;}
ll min3(ll a, ll b, ll c){return (a<=b && a<=c) ? a : b<=c ? b : c;}
ll max3(ll a, ll b, ll c){return (a>=b && a>=c) ? a : b>=c ? b : c;}
ll minn(ll n, ll a[n]){ll b=INF;rep(i,0,n) b=min2(b,a[i]);return b;}
ll maxn(ll n, ll a[n]){ll b=-INF;rep(i,0,n) b=max2(b,a[i]);return b;}
ll ABS(ll a){return a>=0?a:(-a);}
ll POW(ll a, ll b){ll c=1;rep(i,0,b) c*=a;return c;}
ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
ll lcm(ll a,ll b){return a/gcd(a,b)*b;}
ll mod(ll n){return n%=MOD1;}
int upll(const void*a, const void*b){return*(ll*)a<*(ll*)b?-1:*(ll*)a>*(ll*)b?1:0;}
int downll(const void*a, const void*b){return*(ll*)a<*(ll*)b?1:*(ll*)a>*(ll*)b?-1:0;}
void sortup(ll*a,int n){qsort(a,n,sizeof(ll),upll);}
void sortdown(ll*a,int n){qsort(a,n,sizeof(ll),downll);}

typedef struct{ ll aa , bb;}fr;
int cmp1( const void *p, const void *q ) { return ((fr*)p) ->aa - ((fr*)q)->aa;}
/*aのb進数時の桁数*/
ll digits(ll a, ll b){return a/b?1+digits(a/b,b):1;}
/*nをa進数にしたときの、i桁目の数*/
ll a_base2(ll n, ll a, ll i){return i==1?n%a:a_base2(n/a,a,i-1);}

ll RUNRUN[100001];
void runrun(){
    ll a=1,i=1,ok=1;
    while(i<100001){
        ll dig=digits(a,10);
        rep(j,1,dig){
            ll b=a_base2(a,10,j+1), c= a_base2(a,10,j);
            if(ABS(b-c)>1){
                if(b<c){
                    a+=POW(10,j);
                    rep(k,1,j+1){
                        a-=a_base2(a,10,k)*POW(10,k-1);
                    }
                    ok=0;
                    break;
                }
                a+=(b-c-1)*POW(10,j-1);
                ok=2;
                break;
            }
            if(j==dig-1) ok=1;
        }
        // printf("%lld %lld %lld\n",a,ok,i);
        if(ok==1){
            RUNRUN[i]=a;
            a++;
            i++;
        }
    }
}

int main(void){
    // char ;
    ll k;
    scanf("%lld",&k);
    // rep(i,0,n){
    //     scanf("%lld",&[i]);
    // }
    runrun();
    // rep(i,1,k+1){
    //     printf("%lld %lld\n",i,RUNRUN[i]);
    // }
    printf("%lld\n",RUNRUN[k]);
    return 0;
}