Untitled

#include 
#include 
#include 
#include 
#include 
using namespace std;
typedef long long ll;

int main()
{
    int k, n;
    cin >> k >> n;
    int a[n], b[n];
    long long cnt_a[105], cnt_b[105];
    for(int i = 0; i < 105; i++) {
        cnt_a[i] = 0;
        cnt_b[i] = 0;
    }
    for(int i = 0; i < n; i++) {
        cin >> a[i];
        cnt_a[a[i]] += 1;
    }
    for(int j = 0; j < n; j++) {
        cin >> b[j];
        cnt_b[b[j]] += 1;
    }
    long long answer = 0;
    for(int i = 0; i <= 100; i++) {
        for(int j = 0; j <= 100; j++) {
            if(i + j >= k and cnt_a[i] > 0 and cnt_b[j] > 0) {
                answer += cnt_a[i] * cnt_b[j];
            }
        }
    }
    cout << answer << endl;
    return 0;
}

/*

 a[i] + b[j] >= k
 k - a[i]
 
 **/