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  1. #include<bits/stdc++.h>
  2. typedef long long ll;
  3. using namespace std;
  4.  
  5. ll gcd(ll a, ll b) {
  6. 	return !b ? a : gcd(b, a%b);
  7. }
  8.  
  9. bool check(ll x) {
  10. 	if(x <= 10) return false;
  11. 	string s1 = "";
  12. 	while(x) {
  13. 		s1 += x%10 + '0';
  14. 		x /= 10;
  15. 	}
  16. 	reverse(s1.begin(), s1.end());
  17. 	int n = s1.length();
  18. 	string s2 = s1.substr(0, (n+1)/2);
  19. 	string s3 = s1.substr((n+1)/2);
  20. 	ll a = 0, b = 0;
  21. 	for(int i=0; i<s2.length(); ++i)
  22. 		a = a*10 + s2[i] - '0';
  23. 	for(int i=0; i<s3.length(); ++i)
  24. 		b = b*10 + s3[i] - '0';
  25. 	return gcd(a, b) == 1;
  26. }
  27.  
  28. int main() {
  29. 	ll a, b, c;
  30. 	int t; scanf("%d", &t);
  31. 	while(t--) {
  32. 		scanf("%lld%lld", &a, &b);
  33. 		c = -1;
  34. 		for(ll i=b; i>=a; --i) {
  35. 			if(check(i)) {
  36. 				c = i;
  37. 				break;
  38. 			}
  39. 		}
  40. 		printf("%lld\n", c);
  41. 	}
  42. 	return 0;
  43. }
Success #stdin #stdout 0s 4392KB
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https://ideone.com/bLV0UI
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
public

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