#include #define rep(i, a) for (int i = (int)0; i < (int)a; ++i) #define rrep(i, a) for (int i = (int)a - 1; i >= 0; --i) #define REP(i, a, b) for (int i = (int)a; i < (int)b; ++i) #define RREP(i, a, b) for (int i = (int)a - 1; i >= b; --i) #define pb push_back #define eb emplace_back #define all(x) x.begin(), x.end() #define rall(x) x.rbegin(), x.rend() using ll = long long; constexpr ll mod = 1e9 + 7; constexpr ll INF = 1LL << 60; template inline bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; } template inline bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; } ll gcd(ll n, ll m) { ll tmp; while (m != 0) { tmp = n % m; n = m; m = tmp; } return n; } ll lcm(ll n, ll m) { return abs(n) / gcd(n, m) * abs(m); //gl=xy } using namespace std; template< int mod > struct ModInt { int x; ModInt() : x(0) {} ModInt(int64_t y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {} ModInt &operator+=(const ModInt &p) { if((x += p.x) >= mod) x -= mod; return *this; } ModInt &operator-=(const ModInt &p) { if((x += mod - p.x) >= mod) x -= mod; return *this; } ModInt &operator*=(const ModInt &p) { x = (int) (1LL * x * p.x % mod); return *this; } ModInt &operator/=(const ModInt &p) { *this *= p.inverse(); return *this; } ModInt operator-() const { return ModInt(-x); } ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; } ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; } ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; } ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; } bool operator==(const ModInt &p) const { return x == p.x; } bool operator!=(const ModInt &p) const { return x != p.x; } ModInt inverse() const { int a = x, b = mod, u = 1, v = 0, t; while(b > 0) { t = a / b; swap(a -= t * b, b); swap(u -= t * v, v); } return ModInt(u); } ModInt pow(int64_t n) const { ModInt ret(1), mul(x); while(n > 0) { if(n & 1) ret *= mul; mul *= mul; n >>= 1; } return ret; } friend ostream &operator<<(ostream &os, const ModInt &p) { return os << p.x; } friend istream &operator>>(istream &is, ModInt &a) { int64_t t; is >> t; a = ModInt< mod >(t); return (is); } static int get_mod() { return mod; } }; using modint = ModInt< mod >; template struct Linear_imos{ vectorimos,imos2; int n;//要素数 bool flag; Linear_imos(int n):n(n){ flag=false; imos=vector(n+1); imos2=vector(n+1); } void add(int l,int r,T a,T b){//[l,r),公差a,初項bについての加算 imos[l]+=a; imos[r]-=a; imos2[r]-=a*(r-l); imos2[l]+=b+1; imos2[r]-=b+1; } void build(){ flag=true; for(int i=0;i>n; vectora(n); rep(i,n)cin>>a[i]; rep(i,n)if(!a[i]){cout<<0<<"\n";return;} Linear_imosimos(n); modint ans=1; ll right=0; ll sum=1; for(ll left=0;left