#include using namespace std; #define REP(i,a,n) for(int i=(a); i<(int)(n); i++) #define rep(i,n) REP(i,0,n) #define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it) #define ALLOF(c) (c).begin(), (c).end() typedef long long ll; typedef unsigned long long ull; class BIT{ static const int MAX_N = 1 << 21; int n; vector bit; public: BIT(int n_):bit(MAX_N+1){ n = n_; for(int i=0; i0){ s+=bit[i]; i-=i&(-i); } return s; } void add(int i, int x){ while(i<=n){ bit[i]+=x; i+=i&(-i); } } }; const long double PI = 4.0 * atan(1); typedef std::vector< std::complex > VComp; void fft(VComp& a, long double theta){ int n = a.size(); for(int m=n; m>=2; m>>=1){ for(int i=0; i<(m>>1); i++){ std::complex w = exp(i*theta*std::complex(0,1)); for(int j=i; j>1); std::complex x = a[j]-a[k]; a[j] += a[k]; a[k] = w*x; } } theta *= 2; } int i=0; for(int j=1; j>1; k>(i^=k); k>>=1); if(j(0,0)); for(int i=str.length()-1,j=0; i>=0; i--,j++){ ret[j] = str[i] - '0'; } return ret; } VComp VComp_mult(const VComp& a, const VComp& b){ VComp ret(a.size(), std::complex(0,0)); for(int i=0; i= n) n <<= 1; VComp ret1 = str2vec(str1, n); VComp ret2 = str2vec(str2, n); fft(ret1, 2 * PI / n); fft(ret2, 2 * PI / n); VComp ret = VComp_mult(ret1, ret2); fft(ret, -2 * PI / n); //print(ret); std::string ans = ""; int carry = 0; int nonzero_idx = 0; for(int i=0; i 0){ ans += (char)('0' + carry); nonzero_idx = ret.size(); } std::string noleadingzero = ans.substr(0,nonzero_idx+1); std::reverse(noleadingzero.begin(), noleadingzero.end()); return noleadingzero; } class Bignum{ public: Bignum(){} Bignum(string s){ for(int i=0;i=0;i--){ if(d[i]!=0) break; d.pop_back(); } return *this; } int operator[](int i){ return i>=d.size()?0:d[i]; } int size(){ return normalize(),d.size(); } void toZero(){ d.clear(); d.push_front(0); } void toOne(){ d.clear(); d.push_front(1); } Bignum &inc(){ Bignum one("1"); return operator+=(one); } Bignum &operator+=(Bignum n){ int l=max(size(),n.size()); d.resize(l+1,0); for(int c=0,i=0;i<=l;i++) d[i]=(c=d[i]+n[i]+c/10)%10; return normalize(); } Bignum &operator-=(Bignum n){ //assert(size()>=n.size()); for(int c=0,i=0;i=0;i--) d[i]=(c=c%n*10+d[i])/n; return c%n; } Bignum &operator<<=(int n){ for(int i=0;i(Bignum n){ if(size()!=n.size()) return size()>n.size(); for(int i=size()-1;i>=0;i--) if(d[i]!=n[i]) return d[i]>n[i]; return false; } deque d; }; ostream &operator<<(ostream &os, const Bignum &l) { Bignum n=l; if (n.size()==0) os<<0; else for (int i=n.d.size()-1;i>=0;i--) os<> N; vector v; rep(i,N){ int p; cin >> p; v.push_back(p); } BIT bit(1<<20); vector v_num(N); vector v_p(N); Bignum p("1"); for(int i=N-1; i>=0; i--){ ull num = bit.sum(v[i]); v_num[i].toOne(); v_num[i] *= num; v_p[i] = p; p *= N-i; bit.add(v[i], 1); } Bignum ret("1"); rep(j,N){ string tmp1="", tmp2=""; { if(v_num[j].d.size() == 0) tmp1 = "0"; else for (int i=v_num[j].d.size()-1;i>=0;i--) tmp1 += '0' + v_num[j].d[i]; } { if(v_p[j].d.size() == 0) tmp2 = "0"; else for (int i=v_p[j].d.size()-1;i>=0;i--) tmp2 += '0' + v_p[j].d[i]; } string tmp_nump = fft_multi(tmp1, tmp2); Bignum b(tmp_nump); ret += b; } cout << ret << endl; return 0; }