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  1. #include<bits/stdc++.h>
  2. using namespace std;
  3. bool ktsnt(long long n) {
  4.     if(n < 2) return false;
  5.     if(n == 2) return true;
  6.     for(long long i=2; i*i<=n; i++) 
  7.         if(n % i == 0) return false;
  8.     return true;
  9. }
  10. bool isNumber(char ch) {
  11.     return (ch >= '0' && ch <= '9');
  12. }
  13. int main (){
  14.     string s;
  15.     getline(cin, s);
  16.     long long ans = 0;
  17.     for(int i=0; i<s.size(); i++) {
  18.         if(isNumber(s[i])) {
  19.             string so = "";
  20.             int j = i;
  21.             while(j < s.size() && isNumber(s[j])) {
  22.                 so += s[j];
  23.                 j++;
  24.             }
  25.  
  26.             long long num = 0, sz = so.size();
  27.             long long d = 1;
  28.             for(int i=sz-1; i>=0; i--) {
  29.                 num += 1LL*d*(so[i]-'0');
  30.                 d = 1LL*d*10;
  31.             }
  32.  
  33.             //cout << num << '\n';
  34.             if(ktsnt(num)) ans = max(ans, num);
  35.             i = j-1;
  36.         }
  37.     }
  38.     cout << ans << '\n';
  39. }
Success #stdin #stdout 0.01s 5280KB
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https://ideone.com/teLawf
language:
C++14 (gcc 8.3)
created:
237 days ago
visibility:
public

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