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// verification-helper: PROBLEM http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=DPL_5_L #include<bits/stdc++.h> using namespace std; #define call_from_test #include "../../mod/mint.cpp" #include "../../combinatorics/partitiontable.cpp" #undef call_from_test signed main(){ int n,k; scanf("%d %d",&n,&k); PartitionTable<Mint<int>> P(n,k); printf("%d\n",k<=n?P(n-k,k).v:0); return 0; }
#line 1 "test/aoj/DPL_5_L.test.cpp" // verification-helper: PROBLEM http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=DPL_5_L #include<bits/stdc++.h> using namespace std; #define call_from_test #line 1 "mod/mint.cpp" #line 3 "mod/mint.cpp" using namespace std; #endif //BEGIN CUT HERE template<typename T, T MOD = 1000000007> struct Mint{ inline static constexpr T mod = MOD; T v; Mint():v(0){} Mint(signed v):v(v){} Mint(long long t){v=t%MOD;if(v<0) v+=MOD;} Mint pow(long long k){ Mint res(1),tmp(v); while(k){ if(k&1) res*=tmp; tmp*=tmp; k>>=1; } return res; } static Mint add_identity(){return Mint(0);} static Mint mul_identity(){return Mint(1);} Mint inv(){return pow(MOD-2);} Mint& operator+=(Mint a){v+=a.v;if(v>=MOD)v-=MOD;return *this;} Mint& operator-=(Mint a){v+=MOD-a.v;if(v>=MOD)v-=MOD;return *this;} Mint& operator*=(Mint a){v=1LL*v*a.v%MOD;return *this;} Mint& operator/=(Mint a){return (*this)*=a.inv();} Mint operator+(Mint a) const{return Mint(v)+=a;} Mint operator-(Mint a) const{return Mint(v)-=a;} Mint operator*(Mint a) const{return Mint(v)*=a;} Mint operator/(Mint a) const{return Mint(v)/=a;} Mint operator+() const{return *this;} Mint operator-() const{return v?Mint(MOD-v):Mint(v);} bool operator==(const Mint a)const{return v==a.v;} bool operator!=(const Mint a)const{return v!=a.v;} static Mint comb(long long n,int k){ Mint num(1),dom(1); for(int i=0;i<k;i++){ num*=Mint(n-i); dom*=Mint(i+1); } return num/dom; } }; template<typename T, T MOD> ostream& operator<<(ostream &os,Mint<T, MOD> m){os<<m.v;return os;} //END CUT HERE #ifndef call_from_test signed main(){ return 0; } #endif #line 1 "combinatorics/partitiontable.cpp" #line 3 "combinatorics/partitiontable.cpp" using namespace std; #endif //BEGIN CUT HERE template<typename M> struct PartitionTable{ vector< vector<M> > dp; PartitionTable(int h,int w):dp(h+1,vector<M>(w+1,0)){ dp[0][0]=M(1); for(int i=0;i<=h;i++){ for(int j=1;j<=w;j++){ dp[i][j]=dp[i][j-1]; if(i-j>=0) dp[i][j]+=dp[i-j][j]; } } } // put n identical balls into k identical boxes M operator()(int n,int k){return dp[n][k];} // put n identical balls into some boxes M operator()(int n){return dp[n][n];} }; //END CUT HERE #ifndef call_from_test signed main(){ return 0; } #endif #line 9 "test/aoj/DPL_5_L.test.cpp" #undef call_from_test signed main(){ int n,k; scanf("%d %d",&n,&k); PartitionTable<Mint<int>> P(n,k); printf("%d\n",k<=n?P(n-k,k).v:0); return 0; }