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c_cpp
6 months ago
700 B
8
Indexable
Never
#include <bits/stdc++.h>
#define int long long
using namespace std;

const int MAX = 2e5+5;

map<int, int> mp;
int ns[MAX];

signed main() {
  cin.tie(nullptr)->sync_with_stdio(0);

  int n; cin>>n;
  int ans = 0;
  for(int i = 0; i < n; ++i) {
    cin>>ns[i];
    ++mp[ns[i]];
  }
  for(int i = 0; i < n; ++i) {
    if(ns[i] == 1) {
      ans += mp[1] - 1;
      continue;
    }
    ans += mp[1];
    ans += mp[ns[i]] - 1;
    for(int j = 2; j <= (int)sqrt(ns[i])+1; ++j) {
      if(j >= ns[i]) continue;
      if(ns[i] % j == 0) {
        ans += mp[j];
        if(ns[i] / j != j) {
          ans += mp[ns[i] / j];
        }
      }
    }
  }
  cout<<ans<<'\n';
}
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