#include<bits/stdc++.h>
#define ll long long
using namespace std;
template <typename T>
void in(T &x) {
	char c=getchar();
	int f=1;
	while((c>'9'||c<'0')&&c!='-'){
		c=getchar();
	}
	if(c=='-'){
		f=-1;
		c=getchar();
	}
	for(x=0;c>='0'&&c<='9';c=getchar()) {
		x=x*10+c-'0';
	}
	x*=f;
}
double work(double x1,double y11,double x2,double y2){
    return sqrt((x2-x1)*(x2-x1)+(y2-y11)*(y2-y11));
}
int main(){
	double x1,y11,x2,y2,x3,y3;
	in(x1);in(y11);in(x2);in(y2);in(x3);in(y3);
	double x, y, z;
	x=work(x1,y11,x2,y2);
	y=work(x1,y11,x3,y3);
	z=work(x3,y3,x2,y2);
	double ans=x+y+z;
	printf("%.2lf\n",ans);
	return 0;
}

为什么这个样例我老是过不了？

23.234 12.123

-99.99 99.99

-1 -100

正解：489.20

我的答案：407.07