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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. const int maxn = 1e6;
  5. int sieve[maxn];
  6. int main()
  7. {
  8.   for(int i = 0; i < maxn; ++i) {
  9.     sieve[i] = 1;
  10.   }
  11.   for(int i = 2; i < maxn; ++i) {
  12.     for(int j = 2 * i; j < maxn; j += i) {
  13.       sieve[j] = 0;
  14.     }
  15.   }
  16.   sieve[0] = 0;
  17.  
  18.   // for (int i = 0; i < 20; ++i) {
  19.   //   cout << i << " " << sieve[i] << endl;
  20.   // }
  21.   int n;
  22.   cin >> n;
  23.   vector<int> vec(n);
  24.   for (int& a: vec) {
  25.     cin >> a;
  26.   }
  27.  
  28.   bool wfail = 0;
  29.   int cnt = 0;
  30.   for (int i = 0; i <= n - 1; ++i) {
  31.     if (i == n - 1) {
  32.       if (vec[i] == 2 || vec[i] == 0) {
  33.         break;
  34.       }
  35.       if (sieve[vec[i]] == 1) {
  36.         wfail = true;
  37.         break;
  38.       }
  39.     }
  40.  
  41.     if (vec[i] == 2 || sieve[vec[i]] == 0) {
  42.       continue;
  43.     } else {
  44.       vec[i + 1]++;
  45.       cnt++;
  46.       continue;
  47.     }
  48.   }
  49.  
  50.   if (wfail == true) {
  51.     cout << "-1";
  52.   } else {
  53.     cout << cnt;
  54.   }
  55.  
  56. }
Success #stdin #stdout 0.03s 7484KB
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https://ideone.com/XZUSmZ
language:
C++14 (gcc 8.3)
created:
6 days ago
visibility:
public

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