不知道错哪了,要么双循超时20%,要么答案错误20%import java.util.Arrays;import java.util.Scanner;public class Main {static final int mod = (int) (1e9) + 7;public static void main(String[] args) {Scanner in = new Scanner(System.in);int n = in.nextInt();in.nextLine();long a[] = Arrays.stream(in.nextLine().split(" ")).mapToLong(Long::parseLong).toArray();long res = 0;long right = 0;long sum = 0;for (int i = 1; i < n; i++) {right += (i * a[i])%mod;sum += a[i];}sum%=mod;for (int i = 0; i + 1 < n; i++) {// if (a[i] == 0) {// continue;// }// for(int j=i+1;j<n;j++){// res+=(j-i)*a[i]*a[j];// res%=mod;// }res += (a[i]*right) % mod;right-=sum;sum-=a[i+1];res %= mod;}System.out.println(res);}}