Submission #3791339

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Source Code Expand

#include <bits/stdc++.h>

using namespace std;
using ll = long long;
// #define int ll
using PII = pair<ll, ll>;

#define FOR(i, a, n) for (ll i = (ll)a; i < (ll)n; ++i)
#define REP(i, n) FOR(i, 0, n)
#define ALL(x) x.begin(), x.end()

template<typename T> T &chmin(T &a, const T &b) { return a = min(a, b); }
template<typename T> T &chmax(T &a, const T &b) { return a = max(a, b); }
template<typename T> bool IN(T a, T b, T x) { return a<=x&&x<b; }
template<typename T> T ceil(T a, T b) { return a/b + !!(a%b); }

template<typename T> vector<T> make_v(size_t a) { return vector<T>(a); }
template<typename T,typename... Ts>
auto make_v(size_t a,Ts... ts) {
  return vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...));
}
template<typename T,typename V> typename enable_if<is_class<T>::value==0>::type
fill_v(T &t, const V &v) { t=v; }
template<typename T,typename V> typename enable_if<is_class<T>::value!=0>::type
fill_v(T &t, const V &v ) { for(auto &e:t) fill_v(e,v); }

template<class S,class T>
ostream &operator <<(ostream& out,const pair<S,T>& a){
  out<<'('<<a.first<<','<<a.second<<')'; return out;
}
template<typename T>
istream& operator >> (istream& is, vector<T>& vec){
  for(T& x: vec) {is >> x;} return is;
}
template<class T>
ostream &operator <<(ostream& out,const vector<T>& a){
  out<<'['; for(T i: a) {out<<i<<',';} out<<']'; return out;
}

int dx[] = {0, 1, 0, -1}, dy[] = {1, 0, -1, 0}; // DRUL
const int INF = 1<<30;
const ll LLINF = 1LL<<60;
const ll MOD = 1000000007;

// 二分累乗 O(funcの計算量*logE)
template<typename T=ll>
T binpow(T x, ll e, function<T(T,T)> func=[](T a, T b){return a*b%MOD;}, T d=1) {
  T ret = d, p = x;
  while(e > 0) {
    if(e%2 == 0) {p = func(p, p); e /= 2;}
    else {ret = func(ret, p); e--;}
  }
  return ret;
};

struct mint {
  ll x;
  mint(): x(0) { }
  mint(ll y) : x(y>=0 ? y%MOD : y%MOD+MOD) {}
  ll get() const { return x; }
  // e乗
  mint pow(ll e) {
    ll a = 1, p = x;
    while(e > 0) {
      if(e%2 == 0) {p = (p*p) % MOD; e /= 2;}
      else {a = (a*p) % MOD; e--;}
    }
    return mint(a);
  }
  // Comparators
  bool operator <(mint b) { return x < b.x; }
  bool operator >(mint b) { return x > b.x; }
  bool operator<=(mint b) { return x <= b.x; }
  bool operator>=(mint b) { return x >= b.x; }
  bool operator!=(mint b) { return x != b.x; }
  bool operator==(mint b) { return x == b.x; }
  // increment, decrement
  mint operator++() { x++; return *this; }
  mint operator++(signed) { mint t = *this; x++; return t; }
  mint operator--() { x--; return *this; }
  mint operator--(signed) { mint t = *this; x--; return t; }
  // Basic Operations
  mint &operator+=(mint that) {
    x += that.x;
    if(x >= MOD) x -= MOD;
    return *this;
  }
  mint &operator-=(mint that) {
    x -= that.x;
    if(x < 0) x += MOD;
    return *this;
  }
  mint &operator*=(mint that) {
    x = (ll)x * that.x % MOD;
    return *this;
  }
  mint &operator/=(mint that) {
    x = (ll)x * that.pow(MOD-2).x % MOD;
    return *this;
  }
  mint &operator%=(mint that) {
    x = (ll)x % that.x;
    return *this;
  }
  mint operator+(mint that) const { return mint(*this) += that; }
  mint operator-(mint that) const { return mint(*this) -= that; }
  mint operator*(mint that) const { return mint(*this) *= that; }
  mint operator/(mint that) const { return mint(*this) /= that; }
  mint operator%(mint that) const { return mint(*this) %= that; }
};
// Input/Output
ostream &operator<<(ostream& os, mint a) { return os << a.x; }
istream &operator>>(istream& is, mint &a) { return is >> a.x; }

signed main(void)
{
  cin.tie(0);
  ios::sync_with_stdio(false);

  ll n;
  cin >> n;
  vector<PII> a(n);
  REP(i, n) cin >> a[i].second >> a[i].first;

//  REP(i, n) cout << binpow((i+1)*(i+2)%MOD, MOD-2) << endl;

  sort(ALL(a), greater<>());
  vector<mint> w(n), h(n);
  REP(i, n) w[i] = a[i].second, h[i] = a[i].first;

  vector<mint> p(n), q(n);
  p[0] = mint(h[0] * binpow(2, MOD-2));
  FOR(i, 1, n) p[i] = p[i-1] + h[i] * binpow((i+1)*(i+2)%MOD, MOD-2);
  q[0] = mint(binpow(2, MOD-2));
  FOR(i, 1, n) q[i] = q[i-1] + binpow((i+1)*(i+2)%MOD, MOD-2);

  mint ans = 0;
  REP(i, n) ans += (p[i] - q[i] * h[i]) * w[i];
  ans *= 2;
  REP(i, n) ans *= i+1;

  cout << ans << endl;

  return 0;
}

Submission Info

Judge Result