ソースコード
#include<bits/stdc++.h>
#define rep(i,a,b) for(int i=a;i<b;i++)
#define rrep(i,a,b) for(int i=a;i>=b;i--)
#define fore(i,a) for(auto &i:a)
#define all(x) (x).begin(),(x).end()
#pragma GCC optimize ("-O3")
using namespace std; void _main(); int main() { cin.tie(0); ios::sync_with_stdio(false); _main(); }
typedef long long ll; const int inf = INT_MAX / 2; const ll infl = 1LL << 60;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a = b; return 1; } return 0; }
//---------------------------------------------------------------------------------------------------
/*---------------------------------------------------------------------------------------------------
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∧＿∧ （´<_｀ ） Welcome to My Coding Space!
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＼/＿＿＿＿/ （u ⊃
---------------------------------------------------------------------------------------------------*/
int N, K;
//---------------------------------------------------------------------------------------------------
#define CMAX 1010
ll memo[CMAX][CMAX];
int vis[CMAX][CMAX];
ll cmb(int d, int sm) {
if (d < 0 or sm < 0) return 0;
if (d == 0) {
if (sm == 0) return 1;
else return 0;
}
if (vis[d][sm]) return memo[d][sm];
ll res = 0;
rep(i, 0, 10) res += cmb(d - 1, sm - i);
vis[d][sm] = 1;
return memo[d][sm] = res;
}
//---------------------------------------------------------------------------------------------------
void phase2(int d, int n) {
printf("%d", n); N -= n;
rrep(dd, d - 1, 2) rep(nn, 0, 10) {
ll cnt = cmb(dd - 1, N - nn);
if (cnt <= K) K -= cnt;
else {
printf("%d", nn);
N -= nn;
break;
}
}
if(1 < d) printf("%d\n", N);
else printf("\n");
}
//---------------------------------------------------------------------------------------------------
void _main() {
cin >> N >> K;
K--;
rep(d, 1, 1010) rep(n, 1, 10) {
ll cnt = cmb(d - 1, N - n);
if (cnt <= K) K -= cnt;
else {
phase2(d, n);
return;
}
}
}