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  1. #include <bits/stdc++.h>
  2.  
  3. using namespace std;
  4.  
  5. long long N = 1e9 + 7;
  6.  
  7. long long exponentiation(long long base, long long exp)
  8. {
  9.     if (exp == 0)
  10.         return 1;
  11.  
  12.     if (exp == 1)
  13.         return base % N;
  14.  
  15.     long long t = exponentiation(base, exp / 2);
  16.     t = (t * t) % N;
  17.  
  18.     if (exp % 2 == 0)
  19.         return t;
  20.     else
  21.         return ((base % N) * t) % N;
  22. }
  23.  
  24. int main(){
  25.     long long n;
  26.     cin >> n;
  27. 	long long power = exponentiation(2, n) % N;
  28. 	long long multiple = (n - (n%5)) / 5;
  29. 	long long answer;
  30. 	if (n < 4) {
  31. 		answer = 0;
  32. 	}
  33. 	else if (n==4) {
  34. 		answer = 2;
  35. 	}
  36. 	else if (n%5 == 0) {
  37. 		answer = (power - multiple * 2) / 10;
  38. 	}
  39. 	else if (n%5 == 1) {
  40. 		answer = (power - multiple * 4) / 10;
  41. 	}
  42. 	else if (n%5 == 2) {
  43. 		answer = (power - multiple * 8) / 10 + exponentiation(2, multiple - 1);
  44. 	}
  45. 	else if (n%5 == 3) {
  46. 		answer = (power - multiple * 6) / 10;
  47. 	}
  48. 	else if (n%5 == 4) {
  49. 		answer = (power - multiple * 2) / 10;
  50. 	}
  51.  
  52. 	cout << answer;
  53. }
Success #stdin #stdout 0.01s 5308KB
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https://ideone.com/PDtGsK
language:
C++ (gcc 8.3)
created:
39 days ago
visibility:
public

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