计算两点间的距离

#include <iostream>
#include <cstdio>
#include <cmath>
using namespace std;

int main()
{
	double x1, y1, x2, y2, d;
	
	while(~scanf("%lf %lf %lf %lf", &x1, &y1, &x2, &y2))
	{
		d = sqrt((x1 - x2)*(x1 - x2) + (y1 - y2)*(y1 - y2));
		printf("%.2f\n", d);
	}
	
	return 0;
}