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  1. import java.util.*;
  2. import java.lang.*;
  3. import java.io.*;
  4.  
  5. class SumApp
  6. {
  7.    public static Integer scanInteger( Scanner in )
  8.    {
  9.        return ( ( in.hasNextInt() ) ? in.nextInt() : null );
  10.    }
  11.  
  12.    public static void main( String[] args )
  13.    {  
  14.       // рабочие переменные
  15.       Integer n = null;
  16.       int i;
  17.       double s = 0;
  18.       double b, x = 0, xPrev = 0, xPrev2 = 0, xPrev3 = 0;
  19.  
  20.       Scanner in = new Scanner(System.in);
  21.  
  22.       n = scanInteger( in );
  23.  
  24.       in.close(); 
  25.  
  26.  
  27.       if( n == null || n <= 0 )
  28.       {
  29.          System.err.printf("error: missing or out of range: n=%d\n", n);
  30.          return;
  31.       }
  32.  
  33.       // основной цикл сравнения   
  34.       for( i = 1, b = 2; i <= n; i++, b *= 2 )
  35.       {
  36.          if( i > 3 ) 
  37.          {
  38.             xPrev3 = xPrev2;
  39.          }
  40.          if( i > 2 ) 
  41.          {
  42.             xPrev2 = xPrev;   
  43.          }   
  44.          if( i > 1 )
  45.          {
  46.             xPrev = x; 
  47.          }          
  48.          if( i < 4 )
  49.          {
  50.            x = 1;
  51.          }
  52.          else
  53.          {
  54.            x = xPrev + xPrev3;
  55.          }
  56.  
  57.          s += x / b;
  58.       }
  59.  
  60.       // вывод результата
  61.       System.out.printf("result: %f\n", s );
  62.    }
  63. }
Success #stdin #stdout #stderr 0.16s 321344KB
comments (?)
stdin
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-1
stdout
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Standard output is empty
stderr
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error: missing or out of range: n=-1
https://ideone.com/NVdBlc
language:
Java (12.0.1)
created:
8 years ago
visibility:
secret

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