import java.util.*;
 
class Ideone {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int target1 = sc.nextInt();
        int target2 = sc.nextInt();
        int n = sc.nextInt();
 
        int arr[] = new int[n];
        for (int i = 0; i < n; i++) {
            arr[i] = sc.nextInt();
        }
 
        int count = 0;
        for (int k = 1; k < arr.length - 1; k++) {
            int leftCount = countPair(0, k - 1, arr, target1);
            int rightCount = countPair(k, arr.length - 1, arr, target2);
            count += (leftCount * rightCount);
        }
 
        System.out.println(count);
    }
 
    public static int countPair(int start, int end, int arr[], int k) {
        int totalCount = 0;
        while (start < end) {
            int sum = arr[start] + arr[end];
            if (sum > k) {
                totalCount+=(end-start);
                end--; // move right pointer
            } else {
                start++; // move left pointer
            }
        }
        return totalCount;
    }
}

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