求助，只有第4个点AC

#include <bits/stdc++.h>
using namespace std;
double dis(double x1,double y1,double x2,double y2){
    return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
}
int main(){
    double x1,x2,y1,y2,x3,y3;
    cin>>x1>>x2>>y1>>y2>>x3>>y3;
    printf("%.2lf",dis(x1,y1,x2,y2)+dis(x2,y2,x3,y3)+dis(x1,y1,x3,y3));
    return 0;
}