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  1. /**
  2.  *    author:  orzvanh14 ( Độc cô cầu đặc )
  3.  *    created: 23.12.2022 10:08:02
  4.  *    too lazy to update time
  5. **/
  6. // i wants to take ioi
  7. //binhtinhtutinkhongcaycunhungmotkhikhongcontutinnualatuyetvong
  8. #include <bits/stdc++.h>
  9.  
  10. using namespace std;
  11.  
  12. #define int long long
  13. #define nn "\n"
  14. #define pi pair<int, int>
  15. #define fi first
  16. #define se second
  17. #define lb lower_bound
  18. #define ub upper_bound
  19. #define eb emplace_back
  20. #define pb push_back
  21. #define TASK " "
  22.  
  23. #define ms(a, x) memset(a, x, sizeof(a))
  24. #define all(a) a.begin(), a.end()
  25. #define All(a, n) a + 1, a + 1 + n
  26.  
  27. #define LOG 19
  28.  
  29.  
  30. const int INF = 1e18;
  31. const int mod = 1e9+7;
  32. const int N = 1e7  + 5;
  33. const int maxn = 1e3 + 5;
  34. int MOD = 998244353;
  35. int bit[200000];
  36. struct node{
  37. 	int kc, u, hk;
  38. 	bool operator<(const node& other) const {
  39.         return kc > other.kc; 
  40.     }
  41. };
  42. struct edge{
  43. 	int v, w, h;
  44. };
  45. int l, r;
  46. bool p[N];
  47. int uoc[N];
  48. int dem = 0;
  49. void nhap(){
  50.     cin >> l >> r;
  51. }
  52. void sang(){
  53. 	p[1] = 1;
  54. 	for(int i = 2; i < N; i++){
  55. 		if(!p[i]){
  56. 			for(int j = i; j < N; j += i){
  57. 				uoc[j]++;
  58.  
  59. 			}
  60. 			for(int j = i * i; j < N; j += i) p[j] = 1;
  61. 		}
  62. 	}
  63. }
  64. bool ok(int n){
  65. 	string s = to_string(n);
  66. 	int l = 0, r = s.size() - 1;
  67. 	while(l <= r){
  68. 		if(s[l] == s[r]){
  69. 			l++;
  70. 			r--;
  71. 		}
  72. 		else return false;
  73. 	}
  74. 	return true;
  75. }
  76. void solve(){
  77. 	sang();
  78. 	for(int i = l; i <= r; i++){
  79. 		if(ok(i) && uoc[i] >= 3) dem++;
  80. 	}
  81. 	cout << dem << nn;
  82. }
  83. // 0 0 0 0 0 0 0 
  84. signed main() {
  85. 	// freopen("WORK.INP", "r", stdin);
  86. 	// freopen("WORK.OUT", "w", stdout);
  87. 	ios_base::sync_with_stdio(0);
  88. 	cin.tie(0);
  89. 	cout.tie(0);
  90.     nhap();
  91.     solve();
  92. 	return 0;
  93.  
  94. }
  95. // https://i...content-available-to-author-only...e.com/7poJyz
  96. // https://i...content-available-to-author-only...e.com/pScgCp
  97. // https://i...content-available-to-author-only...e.com/DFHWaU
Success #stdin #stdout 0.33s 91616KB
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https://ideone.com/g43SHN
language:
C++14 (gcc 8.3)
created:
2 days ago
visibility:
public

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