#include<bits/stdc++.h>
using namespace std;
 
int ans(vector<int>& v, int k) {
    int c = 0;
    int left = 0;
    int right = v.size() - 1;
 
    while(left < right) {
        if(v[left] + v[right] <= k) {
            c += (right - left);
            left++;
        } else {
            right--; 
        }
    }
    return c;
}
 
int main() {
    int n; 
    cin >> n;
 
    vector<int> v(n);
    for(int i = 0; i < n; i++) {
        cin >> v[i];
    }
 
    int k; 
    cin >> k;
    sort(v.begin(), v.end()); 
 
    cout << ans(v, k) << endl;
    return 0;
}

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NSAKMSAyIDMgNCA1CjUK

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