简单

#include<bits/stdc++.h>
using namespace std;
double dis(double xa, double ya, double xb, double yb) {

return sqrt(pow(xb-xa,2)+pow(yb-ya,2));

}

int main() {
double a,b,c,d,e,f;
cin>>a>>b>>c>>d>>e>>f;
double sum=dis(a,b,c,d)+dis(a,b,e,f)+dis(c,d,e,f);
printf("%.2f",sum);

return 0;

}