十月末补充（？

出租车计价：

#include <stdio.h>
int main()
{
	int x,m,y;
	double z;
	scanf("%d",&x);
	scanf("%d",&m);
	
	if(x>0&&x<=3)
	{
		y=10;
	}
	else if((x-3)>0&&(x-3)<=10)
	{
		y=10+2*(x-3);
	}
	else if(x>13)
	{
		y=3*(x-13)+10+2*10;
		
	}
	else
	{
		return 1;
	}
	
	
	if(m>=5)
	{
	z=(m/5.0)*2.0;
	}
	else
	{
		z=0.0;
	}
	double fee=y+z;             //注意把z、fee写成double类型的 才好四舍五入
	printf("%.0f",fee);
	
	return 0;
}

/*
#include <stdio.h>

int countdigit(int num, int digit);

int main() 
{
    int n;

    scanf("%d", &n);

    int count = assistant(n, 2);

    printf("%d", count);

    return 0;
}

int digit(int num, int digit) 
{
    int count = 0;

    if (num == 0 && digit == 0) 
	{
        return 1; 
    }

    while (num > 0) 
	{
        int last = num % 10;
        if (last == digit) 
		{
            count++;
        }
        num /= 10; 
    }

    return count;
}
*/

/*
#include <stdio.h>

double real,imag;    //全局变量
void prod(double real1,double imag1,double real2,double imag2);
void add(double real1,double imag1,double real2,double imag2);
int main()
{
  double real1,real2,imag1,imag2;
  scanf("%lf %lf",&real1,&imag1);
  scanf("%lf %lf",&real2,&imag2);
  add(real1,imag1,real2,imag2);
  printf("%.2f+%.2fi\n",real,imag);
  prod(real1,imag1,real2,imag2);
  printf("%.2f+%.2fi\n",real,imag);
  return 0;
}

void prod(double real1,double imag1,double real2,double imag2)
{
  real=real1*real2-imag1*imag2;
  imag=real1*imag2+real2*imag1;
  return;
}
void add(double real1,double imag1,double real2,double imag2)
{
  real=real1+real2;
  imag=imag1+imag2;
  return;
}
*/


/*
#include <stdio.h>
int main()
{
	int choice;
	double cash=0.0;
	double value;
	void income(double number,double cash),explend(double number,double cash);
	
	scanf("%d",&choice);
	if(choice!=0)
	{
		if(choice==1||choice==2)
		{
			scanf("%lf",&value);
			if(choice==1)
			{
				income(value);
				
			}
			else
			{
				expend(value);
				
			}
			printf("%.2f",cash);
			scanf("%d",&choice);
			
		}
		else(choice==0)
		{
			return 1;
		}
	}
	return 0;
	
} 

void income(double number,double cash)
{
	return (cash+=number);
}
void explend(double number,double cash)
{
	return (cash-=number);
}
*/

/*
#include <stdio.h>
int main()
{
  char ch;
  ch=getchar();
  while(ch!='\n')
  {
    if(ch>='A'&&ch<='Z')
    {
      ch=ch-'A'+'a';
    }
    else if(ch>='a'&&ch<='z')
    {
        ch=ch-'a'+'A';
	}
      putchar(ch);
      ch=getchar();
    }
  }
  return 0;
} 

#include <stdio.h>
int main()
{
  char ch;
  while((ch=getchar())!=EOF)
  {
    if(ch>='A'&&ch<='Z')
    {
      ch=ch-'A'+'a';
    }
    else if (ch>='a'&&ch<='z')
    {
      ch=ch-'a'+'A';
    }
      putchar(ch);
    }
  }
  return 0;
} 
*/

/*
#include <stdio.h>
int main()
{
  int word,count;
  char ch;
  word=count=0;
  while((ch=getchar())!=EOF)
  {
    if(ch==' ')
    {
      word=0;
    }
    else if(word==0)
    {
      word=1;
      count++;
    }
  }
  printf("%d",count);
  return 0;
}

*/


#include <stdio.h>
#include <math.h>

double distance(double x1,double x2,double y1,double y2)
{
	double dist;
	dist = sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
	return dist;
}


int main()
{
	double x1,y1,x2,y2;

	scanf("%lf %lf",&x1,&y1);
	scanf("%lf %lf",&x2,&y2);
	
	double dist=distance(x1,x2,y1,y2);
	printf("%.2f",dist);
	
	return 0;
}