Language: C++

#include "bits/stdc++.h"
using namespace std;
using     ll=long long;
using    vll=vector<   ll>;
using   vvll=vector<  vll>;
using  vvvll=vector< vvll>;
using vvvvll=vector<vvvll>;
constexpr ll INF = 1LL << 60;
struct Fast{ //cin,cout高速化のおまじない＋桁数指定
	Fast(){ cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(std::numeric_limits<double>::max_digits10); }
} fast;
#define rep(i, S, E)  for (ll i = (S); i <= (E); i++)
#define dep(i, E, S)  for (ll i = (E); i >= (S); i--)
#define each(e, v) for (auto&& e : v)
#define ALL(v) (v).begin(), (v).end()
#define RALL(v) (v).rbegin(), (v).rend()
template<class T> inline bool chmax(T &a, T b) { if (a < b) { a = b; return true; }return false; }
template<class T> inline bool chmin(T &a, T b) { if (a > b) { a = b; return true; }return false; }
template<class T> inline T MaxE(vector<T>&v,ll S,ll E){ T m=v[S]; rep(i,S,E)chmax(m,v[i]); return m; }
template<class T> inline T MinE(vector<T>&v,ll S,ll E){ T m=v[S]; rep(i,S,E)chmin(m,v[i]); return m; }
template<class T> inline T MaxE(vector<T> &v) { return MaxE(v,0,(ll)v.size()-1); }
template<class T> inline T MinE(vector<T> &v) { return MinE(v,0,(ll)v.size()-1); }
template<class T> inline T Sum(vector<T> &v,ll S,ll E){ T s=T(); rep(i,S,E)s+=v[i]; return s; }
template<class T> inline T Sum(vector<T> &v) { return Sum(v,0,v.size()-1); }
template<class T> inline ll sz(T &v){ return (ll)v.size(); }
template<class T> inline T POW(T a, ll n){ T r=1; for (; n>0; n>>=1, a*=a){ if (n&1)r*=a; } return r; }
inline ll POW(int a, ll n){ return POW((ll)a, n); }
inline ll CEIL(ll a, ll b){ return (a+b-1)/b; }

template<ll MOD> struct mll_{
	ll val;
	mll_(ll v = 0): val(v % MOD){ if (val < 0) val += MOD; }
	mll_ operator - () const { return -val; }
	mll_ operator + (const mll_ &b) const { return val + b.val; }
	mll_ operator - (const mll_ &b) const { return val - b.val; }
	mll_ operator * (const mll_ &b) const { return val * b.val; }
	mll_ operator / (const mll_ &b) const { return mll_(*this) /= b; }
	mll_ operator + (ll b) const { return *this + mll_(b); }
	mll_ operator - (ll b) const { return *this - mll_(b); }
	mll_ operator * (ll b) const { return *this * mll_(b); }
	friend mll_ operator + (ll a,const mll_ &b) { return b + a; }
	friend mll_ operator - (ll a,const mll_ &b) { return -b + a; }
	friend mll_ operator * (ll a,const mll_ &b) { return b * a; }
	friend mll_ operator / (ll a,const mll_ &b) { return mll_(a)/b; }
	mll_ &operator += (const mll_ &b) { val=(val+b.val)%MOD; return *this; }
	mll_ &operator -= (const mll_ &b) { val=(val+MOD-b.val)%MOD; return *this; }
	mll_ &operator *= (const mll_ &b) { val=(val*b.val)%MOD; return *this; }
	mll_ &operator /= (const mll_ &b) {
		ll c=b.val,d=MOD,u=1,v=0;
		while (d){
			ll t = c / d;
			c -= t * d; swap(c,d);
			u -= t * v; swap(u,v);
		}
		val = val * u % MOD;
		if (val < 0) val += MOD;
		return *this;
	}
	mll_ &operator += (ll b) { return *this += mll_(b); }
	mll_ &operator -= (ll b) { return *this -= mll_(b); }
	mll_ &operator *= (ll b) { return *this *= mll_(b); }
	mll_ &operator /= (ll b) { return *this /= mll_(b); }
	bool operator == (const mll_ &b) { return val == b.val; }
	bool operator != (const mll_ &b) { return val != b.val; }
	bool operator == (ll b) { return *this == mll_(b); }
	bool operator != (ll b) { return *this != mll_(b); }
	friend bool operator == (ll a,const mll_ &b) { return mll_(a) == b.val; }
	friend bool operator != (ll a,const mll_ &b) { return mll_(a) != b.val; }
	friend ostream &operator << (ostream &os,const mll_ &a) { return os << a.val; }
	friend istream &operator >> (istream &is,mll_ &a) { return is >> a.val; }
	static mll_ Combination(ll a,ll b){
		chmin(b,a-b);
		if (b<0) return mll_(0);
		mll_ c = 1;
		REP(i,b) c *= a-i;
		REP(i,b) c /= i+1;
		return c;
	}
};
using mll = mll_<1000000007LL>;
using vmll    = std::vector<mll>;
using vvmll   = std::vector<vmll>;
using vvvmll  = std::vector<vvmll>;
using vvvvmll = std::vector<vvvmll>;


void solve()
{
	ll n,m;  cin >> n >> m;
	vector<ll> x(n);  rep(i,0,n-1){ ll x_; cin>>x_; x[i]=x_; }
	vector<ll> y(m);  rep(i,0,m-1){ ll y_; cin>>y_; y[i]=y_; }

	mll smx=0;
	rep(i,1,n-1){
		mll s=(x[i]-x[i-1]);
		s*=i;
		s*=n-i;
		smx+=s;
	}

	mll smy=0;
	rep(i,1,m-1){
		mll s=(y[i]-y[i-1]);
		s*=i;
		s*=m-i;
		smy+=s;
	}
	mll ans=smx*smy;
	cout << ans << '\n';
}


int main(){
#if 1
	solve();
#else
	ll t;  cin >> t;
	rep(i, 0, t-1){
		solve();
	}
#endif
	return 0;
}


Compiler output:
a.cc: In static member function 'static mll_<MOD> mll_<MOD>::Combination(ll, ll)':
a.cc:75:21: error: 'i' was not declared in this scope
   75 |                 REP(i,b) c *= a-i;
      |                     ^
a.cc:75:17: error: there are no arguments to 'REP' that depend on a template parameter, so a declaration of 'REP' must be available [-fpermissive]
   75 |                 REP(i,b) c *= a-i;
      |                 ^~~
a.cc:75:17: note: (if you use '-fpermissive', G++ will accept your code, but allowing the use of an undeclared name is deprecated)
a.cc:75:26: error: expected ';' before 'c'
   75 |                 REP(i,b) c *= a-i;
      |                          ^
a.cc:76:17: error: there are no arguments to 'REP' that depend on a template parameter, so a declaration of 'REP' must be available [-fpermissive]
   76 |                 REP(i,b) c /= i+1;
      |                 ^~~
a.cc:76:26: error: expected ';' before 'c'
   76 |                 REP(i,b) c /= i+1;
      |                          ^