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  1. #include <iostream>
  2. using namespace std;
  3.  
  4. int main() {
  5.     ios::sync_with_stdio(false);
  6.     cin.tie(nullptr);
  7.  
  8.     int n;
  9.     if (!(cin >> n)) return 0;
  10.     if (n == 0 || n == 1) {
  11.         cout << 1;
  12.         return 0;
  13.     }
  14.  
  15.     int a = 1; // f(0)
  16.     int b = 1; // f(1)
  17.     for (int i = 2; i <= n; ++i) {
  18.         int c = a + b; // f(i) = f(i-1) + f(i-2)
  19.         a = b;
  20.         b = c;
  21.     }
  22.     cout << b;
  23.     return 0;
  24. }
Success #stdin #stdout 0.01s 5284KB
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Standard output is empty
https://ideone.com/9pLsKo
language:
C++ (gcc 8.3)
created:
3 days ago
visibility:
public

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