* * *#include <cstdio>
#include <iostream>
#include <cstring>
#include <algorithm>
#include <cmath>
using namespace std;
int m,n;
long long ans;
const int p=10007;
struct node{
	int num,color,n;
}a[100010];
long long sum[100010][3];//统计相同颜色相同奇偶的格子的数字和
long long cnt[100010][3];//统计k
inline int Read(){
    int res=0,ch,flag=0;
    if((ch=getchar())=='-')
        flag=1;
    else if(ch>='0'&&ch<='9')
        res=ch-'0';
    while((ch=getchar())>='0'&&ch<='9')
        res=res*10+ch-'0';
    return flag?-res:res;
}
inline void Write(int a){
    if(a>9)
        Write(a/10);
    putchar(a%10+'0');
}
int main(){
	n=Read();m=Read();
	for (int i=1;i<=n;i++){
		a[i].num=Read();
		a[i].n=i;
	}
	for (int i=1;i<=n;i++){
		a[i].color=Read();
		sum[a[i].color][i%2]=sum[a[i].color][i%2]%p+a[i].num%p;
		sum[a[i].color][i%2]%=p;
		cnt[a[i].color][i%2]++;
	}
	for (int i=1;i<=n;i++){
		if (cnt[a[i].color][i%2]>1){
			ans=ans%p+i%p*(a[i].num%p*(cnt[a[i].color][i%2]-2%p)+sum[a[i].color][i%2]%p)%p;//套用推的式子
			ans%=p;
		}
	}
	cout<<ans<<endl;
	return 0;
}
 * * *

求和

较快

 * * #include <cstdio>
     #include <iostream>
     #include <cstring>
     #include <algorithm>
     #include <cmath>
