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  1. #include <iostream>
  2.  
  3. using namespace std;
  4.  
  5. int main()
  6. {
  7.     int n;
  8.     cin >> n;
  9.     float s = 0;
  10.     int i = 1, d = 1;
  11.     while(i <= n)
  12.     {
  13.         s += i*d;
  14.         i++; d = -d;
  15.     }
  16.     cout << s;
  17. }
  18.  
Success #stdin #stdout 0.01s 5276KB
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https://ideone.com/930Y8C
B2: S(n) = 1 - 2 + 3 - 4 + … + (-1)^(n+1) * n (n > 0)
language:
C++14 (gcc 8.3)
created:
23 hours ago
visibility:
public

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