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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. const int N = 1e6 + 5;
  5.  
  6. bool is_prime[N];
  7. int a[N];
  8. long long prefix[N];
  9.  
  10. void sieve(int n) {
  11.     fill(is_prime, is_prime + n + 1, true);
  12.     is_prime[0] = is_prime[1] = false;
  13.     for (int i = 2; i * i <= n; ++i) {
  14.         if (is_prime[i]) {
  15.             for (int j = i * i; j <= n; j += i)
  16.                 is_prime[j] = false;
  17.         }
  18.     }
  19. }
  20.  
  21. int main() {
  22.     ios::sync_with_stdio(false);
  23.     cin.tie(nullptr);
  24.  
  25.     freopen("EASYSEQ.INP", "r", stdin);
  26.     freopen("EASYSEQ.OUT", "w", stdout);
  27.  
  28.     int n;
  29.     cin >> n;
  30.     for (int i = 1; i <= n; ++i) cin >> a[i];
  31.  
  32.     // Tính mảng tổng cộng dồn
  33.     prefix[0] = 0;
  34.     for (int i = 1; i <= n; ++i)
  35.         prefix[i] = prefix[i - 1] + a[i];
  36.  
  37.     // Đánh dấu các chỉ số nguyên tố
  38.     sieve(n);
  39.  
  40.     long long res = LLONG_MIN;
  41.  
  42.     for (int L = 2; L <= n; ++L) {
  43.         if (!is_prime[L]) continue;
  44.         for (int R = L; R <= n; ++R) {
  45.             if (!is_prime[R]) continue;
  46.             long long total = prefix[R] - prefix[L - 1];
  47.             res = max(res, total);
  48.         }
  49.     }
  50.  
  51.     cout << res << '\n';
  52.  
  53.     return 0;
  54. }
  55.  
Success #stdin #stdout 0.01s 7860KB
comments (?)
stdin 
Standard input is empty
stdout 
Standard output is empty
https://ideone.com/8O6XgK
language:
C++ (gcc 8.3)
created:
4 days ago
visibility:
public

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