Pair of Topics

#include <bits/stdc++.h>
#pragma GCC optimize("0")
using namespace std;

#define cin(vec) for(auto& i : vec) cin >> i
#define cin_2d(vec, n, m) for(int i = 0; i < n; i++) for(int j = 0; j < m && cin >> vec[i][j]; j++);
#define cout(vec) for(auto& i : vec) cout << i << " "; cout << "\n";
#define cout_2d(vec, n, m) for(int i = 0; i < n; i++, cout << "\n") for(int j = 0; j < m && cout << vec[i][j] << " "; j++);
#define cout_map(mp) for(auto& [f, s] : mp) cout << f << "  " << s << "\n";
#define Time cerr << "Time Taken: " << (float)clock() / CLOCKS_PER_SEC << " Secs" << "\n";
#define fixed(n) fixed << setprecision(n)
#define ceil(n, m) (((n) / (m)) + ((n) % (m) ? 1 : 0))
#define fill(vec, value) memset(vec, value, sizeof(vec));
#define Num_of_Digits(n) ((int)log10(n)+1)
#define all(vec) vec.begin(),vec.end()
#define rall(vec) vec.rbegin(),vec.rend()
#define sz(x) int(x.size())
#define TC int t; cin >> t;   while(t--)
#define fi first
#define se second
#define Pair pair < int, int >
#define ll long long
#define ull unsigned long long
#define Mod  1'000'000'007
#define INF 2'000'000'000
#define EPS 1e-9
#define PI acos(-1)

void Code_Crush(){
  ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
  #ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout);
  #endif
}

int main(){
  Code_Crush();
  int n;  cin >> n;
  ll res = 0;
  vector < int >  a(n), b(n), diff(n);
  cin(a);
  cin(b);
  for(int i = 0; i < n; i++)
    diff[i] = a[i] - b[i];
  sort (all(diff));
  for(int i = 0; i < n; i++){
      if(diff[i] > 0){
          ll lb = lower_bound(all(diff), 1 - diff[i]) - diff.begin();
          res += i - lb;
      }
  }
  cout << res;
  Time
  return 0;
}