#include using namespace std; #define FOR(i,a,b) for(int i=(a);i<(b);++i) #define REP(i,n) FOR(i,0,n) #define ALL(v) begin(v),end(v) template inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; } template inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; } using ll = long long; using pii = pair; constexpr ll INF = 1ll<<30; constexpr ll longINF = 1ll<<60; constexpr ll MOD = 1000000007; constexpr bool debug = false; //---------------------------------// int main() { ll N, S; cin >> N >> S; vector fact(S + 1); fact[0] = 1; FOR(i, 1, fact.size()) fact[i] = fact[i - 1] * i; vector perm(S); vector done(S); ll cur = N; REP(i, perm.size()) { int rank = cur / fact[S - i - 1]; REP(j, done.size()) { if (done[j]) continue; if (rank == 0) { perm[i] = j; done[j] = true; break; } --rank; } cur = cur % fact[S - i - 1]; } vector rev(S); done.assign(S, false); REP(i, perm.size()) rev[perm[i]] = i; ll ans = 0; REP(i, rev.size()) { int rank = 0; REP(j, rev[i]) if (!done[j]) ++rank; done[rev[i]] = true; ans += rank * fact[S - i - 1]; } cout << ans << endl; }