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  1. #include<iostream>
  2.  
  3. bool isPrime(int x) {
  4.     if(x < 2) return false;
  5.     for(int i = 2; i * i <= x; ++i) {
  6.         if(x % i == 0) return false;
  7.     }
  8.     return true;
  9. }
  10.  
  11. int main() {
  12.     freopen("SNT.INP", "r", stdin);
  13.     freopen("SNT.OUT", "w", stdout);
  14.  
  15.     std::string S;
  16.     std::cin >> S;
  17.  
  18.     S = S + 'a';
  19.     int num = 0, res = -1;
  20.  
  21.     for(int i = 0; i < S.length(); ++i) {
  22.         if('0' <= S[i] && S[i] <= '9') {
  23.             num = num * 10 + (S[i] - '0');
  24.         }
  25.         else {
  26.             if(isPrime(num)) res = std::max(res, num);
  27.             num = 0;
  28.         }
  29.     }
  30.  
  31.     std::cout << res;
  32.  
  33.     return 0;
  34. }
  35.  
Success #stdin #stdout 0.01s 5320KB
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https://ideone.com/UA3wWh
language:
C++ (gcc 8.3)
created:
3 days ago
visibility:
public

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