家人们谁懂啊，80分求助！！！

#include<bits/stdc++.h>
using namespace std;

double dis(int x1,int y1,int x2,int y2){
    return sqrt(abs((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1)));
}
int main(){
    double x1,y1,x2,y2,x3,y3;
    cin>> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
    cout<< fixed << setprecision(2) << dis(x1,y1,x2,y2)+dis(x2,y2,x3,y3)+dis(x3,y3,x1,y1);
    return 0;
}