import java.util.Arrays; import java.util.Scanner; /** * 奶牛编号 * @author WangYixin * */ public class Main2 { public static void main(String[] args) { // TODO Auto-generated method stub Scanner sc = new Scanner(System.in); while(sc.hasNext()){ int n = sc.nextInt(); //假设arr非降序，否则需要对齐排序 int[] arr = new int[n]; for(int i= 0;i<n;i++){ arr[i] = sc.nextInt(); } //!!!!新增加排序 Arrays.sort(arr); long[] f = new long[n]; f[0] = arr[0]; for(int i=1;i<n;i++){ //不影响前面+影响前面 long front = (arr[i]-arr[i-1])*f[i-1] % 1000000007; long after = f[i-1]*(arr[i-1]- i) ; f[i] = (front + after)% 1000000007; } System.out.println(f[n-1]); } } }