1.3-16:计算线段长度

#include<iostream>
#include<iomanip>
#include<math.h>
using namespace std;
int main()
{
	double xa,ya,xb,yb;
	cin>>xa>>ya>>xb>>yb;
	double c=sqrt((xa-xb)*(xa-xb)+(ya-yb)*(ya-yb));
	cout<<fixed<<setprecision(3)<<c;
	return 0;
}