```java
import java.util.Arrays;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int a = sc.nextInt();
int aa[] = new int[a];
for (int i = 0; i < a; i++) {
int q = sc.nextInt();
if (q >= 0) {
aa[i] = q;
} else break;
}
int sum = 0;
for (int i = 0; i < aa.length; i++) {
for (int j = i + 1; j < aa.length; j++) {
if (Arrays.binarySearch(aa, aa[i] + aa[j]) >= 0) {
sum++;
}
}
}
System.out.println(sum);
}
}
```
by Reikiaz @ 2019-07-13 10:04:10
乐意效劳，但请原谅我这个蒟蒻看不懂java【捂脸哭】
by 江南小巫 @ 2019-07-13 10:10:14