text: #include <stdio.h>
  #include <stdlib.h>
  //#include <genlib.h>
  
  int abs(int n);
  /**
   * output:
   * 
   */
  int main()
  {
      int number;
      printf("please input one negative number, get absolute value :");
  
      scanf("%d", &number);
      printf("your input is %d, it's abs = %d .", number, abs(number));
  
      getchar();
      return 0;
  }
  
  int abs(int n)
  {
      if (n > 0)
      {
          return n;
      }
      else
      {
          return -n;
      }
  }