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  1. #include<bits/stdc++.h>
  2. #define f1(i, n) for(ll i=1;i<=n;++i)
  3. #define f0(i, n) for(ll i=0;i<n;++i)
  4. #define ull unsigned long long
  5. #define ll long long
  6. #define rev(a) reverse(a.begin(),a.end())
  7. #define all(x) x.begin(),x.end()
  8. #define so(A, n) sort(A+1, A+n+1)
  9. using namespace std;
  10. const int maxn = 200010;
  11. const int N = 5e6;
  12. int D[N + 1];
  13. void Sieve() {
  14. 	D[0] = D[1] = 1;
  15. 	int k = sqrt(N);
  16. 	for (int i = 1; i <= k; ++i) {
  17. 		if (D[i] == 0) {
  18. 			for (int j = i; j <= N / i; ++j) {
  19. 				D[i * j] = 1;
  20. 			}
  21. 		}
  22. 	}
  23. }
  24.  
  25. int main()
  26. {
  27. 	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  28. 	Sieve();
  29. 	string s;
  30. 	cin >> s;
  31. 	int j = 0;
  32. 	vector<string> v;
  33. 	while (j < s.size()) {
  34. 		if (s[j] >= '0' && s[j] <= '9') {
  35. 			string motcaigiday = "";
  36. 			while (s[j] >= '0' && s[j] <= '9' && j < s.size()) {
  37. 				motcaigiday += s[j];
  38. 				++j;
  39. 			}
  40. 			v.push_back(motcaigiday);
  41. 		}
  42. 		++j;
  43. 	}
  44. 	int ma = 0;
  45. 	for (int it = 0; it < v.size(); ++it) {
  46. 		for (int i = 0; i < v[it].size(); ++i) {
  47. 			for (int j = i; j < v[it].size(); ++j) {
  48. 				if (j - i + 1 > 6) break;
  49. 				string num = v[it].substr(i, j - i + 1);
  50. 				int n = stoll(num);
  51. 				if (n > 5e6) break;
  52. 				if (D[n] == 0) {
  53. 					ma = max(ma, n);
  54. 				}
  55. 			}
  56. 		}
  57. 	}
  58. 	cout << ma;
  59. 	return 0;
  60. }
  61.  
  62.  
Success #stdin #stdout 0.06s 23160KB
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https://ideone.com/3QxFRf
language:
C++14 (gcc 8.3)
created:
13 days ago
visibility:
public

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