代码：

#include<bits/stdc++.h>
using namespace std;
double x1,x2,x3,y1,y2,y3,h;
double mm(double a){
	return a*a;
}
double cat(double a1,double b1,double a2,double b2){
	double n;
	n=sqrt(mm(a2-a1)+mm(b2-b1));
	return n;
}
int main(){
	scanf("%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&y2,&x3,&y3);
	h+=cat(x1,y1,x2,y2);
	h+=cat(x1,y1,x3,y3);
	h+=cat(x2,y2,x3,y3);
	printf("%.2lf",h);
    return 0;
} 

c⌒っﾟДﾟ)っ求救