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  1. #include<bits/stdc++.h>
  2. using namespace std;
  3. bool ktsnt(int n) {
  4.     if(n < 2) return false;
  5.     if(n == 2) return true;
  6.     for(int 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; cin >> s;
  15.     int ans = 0;
  16.     for(int i=0; i<s.size(); i++) {
  17.         if(isNumber(s[i])) {
  18.             string so = "";
  19.             int j = i;
  20.             while(j < s.size() && isNumber(s[j])) {
  21.                 so += s[j];
  22.                 j++;
  23.             }
  24.  
  25.             int num = 0, sz = so.size();
  26.             for(int i=sz-1; i>=0; i--)
  27.                 num += pow(10, sz-i-1)*(so[i]-'0');
  28.  
  29.             if(ktsnt(num)) ans = max(ans, num);
  30.             i = j-1;
  31.         }
  32.     }
  33.     cout << ans << '\n';
  34. }
Success #stdin #stdout 0s 5300KB
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https://ideone.com/F7hXg7
language:
C++14 (gcc 8.3)
created:
237 days ago
visibility:
public

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