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  1.  
  2. #include <iostream>
  3. #include <iomanip>
  4. #include<cmath>
  5. using namespace std;
  6.  
  7. int main()
  8. {
  9.  
  10.  
  11.  
  12.  
  13.    /* double r;
  14.     double pi = 3.141592653;
  15.  
  16.     cin >> r;
  17.     cout << fixed << setprecision(9) << (pi * r * r);
  18.     */
  19.  
  20.  
  21.  
  22.    // long long x;
  23.    // long long  y;
  24.    // int a , b;
  25.    // cin >> x >> y;
  26.    // a = x % 10;
  27.    // b = y % 10;
  28.    // cout << a + b;
  29.  
  30.  
  31.  
  32.    /* long long x, y, n;
  33.     cin >> n >> x >> y;
  34.     cout << n * (y - x) << endl;
  35.     */
  36.  
  37.     /*long long x, y;
  38.     cin >> x >> y;
  39.     cout << x / y;
  40.     */
  41.  
  42.    /* cout << fixed << setprecision(6);
  43.     double n, r;
  44.     double pi = 3.141592;
  45.  
  46.     cin >> n >> r;
  47.     cout << fixed << setprecision(6) << (pi * r * r) - (n * n);
  48.     */
  49.  
  50.    /*double x, y;
  51.     cin >> x >> y;
  52.     long long ans = ceil(x / y);
  53.     cout << ans;
  54.     */
  55.     /*long long n;
  56.     cin >> n;
  57.     cout << 0 << " " << 0;
  58.     */
  59.  
  60.     /*double a, b;
  61.     cin >> a >> b;
  62.     cout << "floor " << a << " / " << b << " = " << floor(a / b) << endl;
  63.     cout << "ceil " << a << " / " << b << " = " << ceil(a / b) << endl;
  64.     cout << "round " << a << " / " << b << " = " << round(a / b) << endl;
  65.     */
  66.  
  67.    /* long long n, sum;
  68.     cin >> n;
  69.     sum = (n * (n + 1)) / 2;
  70.     cout << sum; */
  71.  
  72.    /* double a, b, c, x;
  73.     cin >> a >> b >> c;
  74.     x = ((2 * a) + (3 * b)) * (5 * c);
  75.     cout << fixed << setprecision(6) << x;
  76.     */
  77.  
  78.  
  79.    /* long long n;
  80.     cin >> n;
  81.     cout << n;
  82.     */
  83.  
  84.  
  85.     double r;
  86.     double pi = 3.141592;
  87.  
  88.     cin >> r;
  89.  
  90.     cout << fixed << setprecision(4) << (pi * r * r) + (0.5 * 2 * r * 1.732050 * r) - (0.5 * r * (3.141592 / 3));
  91.  
  92.  
  93.  
  94.  
  95.  
  96.  
  97.  
  98.  
  99.  
  100.     return 0;
  101. }
  102.  
  103.  
Success #stdin #stdout 0.01s 5292KB
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https://ideone.com/FY9p3n
language:
C++ (gcc 8.3)
created:
15 hours ago
visibility:
public

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