Submission #1234952

#	Time	Username	Problem	Language	Result	Execution time	Memory
1234952		hq77	Fancy Fence (CEOI20_fancyfence)	C++20	15 / 100	50 ms	468 KiB

fancyfence

// Source: https://usaco.guide/general/io

#include <bits/stdc++.h>
#include <cctype>
using namespace std;
#define ll long long
const int MOD=1e9+7;
int main() {
	ll n;cin>>n;
    // vector<int>h(n);
    ll sum=0;
    ll h,w;
    for(int i=0;i<n;i++){
        cin>>h;
    }
    for(int i=0;i<n;i++){
        cin>>w;
        sum+=w;
    }
    // ll s=0;
    // for(int i=sum;i>=1;i--){
    //     for(int j=h;j>=1;j--){
    //         // cout<<i<<" "<<j<<endl;
    //         s+=(((i%MOD)*(j%MOD))%MOD);
    //         s%=MOD;
    //     }
    // }
    // cout<<s<<endl;
    sum=(sum%MOD) * ((sum+1)%MOD);sum/=2;
    sum%=MOD;
    h=(h%MOD)*((h+1)%MOD);h/=2;
    h%=MOD;
    ll ans=(h*sum)%MOD;
    
    cout<<ans%MOD;
}

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