P2671 [NOIP2015 普及组] 求和

#include<bits/stdc++.h>
#define ll long long
#define f(a,b,c) for(ll a=b;a<=c;++a)
#define F(a,b,c) for(ll a=b;a>=c;--a)
using namespace std;
ll m,n,x,y,ans;
ll a[100005],b[100005],f[100005];
ll a1[1000005][10],a2[1000005][10],a3[1000005][10],a4[1000005][10];
int main()
{
	ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
	cin>>n>>m;
	f(i,1,n) cin>>a[i];
	f(i,1,n) cin>>b[i];
	f(i,1,n)
	{
		y=i%2;
		ans+=a1[b[i]][y];
		ans%=10007;
		ans+=a2[b[i]][y]*a[i];
		ans%=10007;
		ans+=a3[b[i]][y]*i;
		ans%=10007;
		ans+=a4[b[i]][y]*i%10007*a[i]%100007;
		ans%=10007;
		a1[b[i]][y]+=1LL*i*a[i]%10007;
		a1[b[i]][y]%=10007;
		a2[b[i]][y]+=i;
		a2[b[i]][y]%=10007;
		a3[b[i]][y]+=a[i];
		a3[b[i]][y]%=10007;
		++a4[b[i]][y];
		a4[b[i]][y]%=10007;
	}
	cout<<ans;
	return 0;
}