为什么每次都是80分

#include<bits/stdc++.h>
using namespace std;
double calc(double a, double b, double c, double d){
    return sqrt(abs((c-a)*(c-a))+abs((d-b)*(d-b)));  
}
int main(){
    int x1, y1, x2, y2, x3, y3;
    double length=0.0;
    cin>>x1>>y1;
    cin>>x2>>y2;
    cin>>x3>>y3;
    length+=calc(x1,y1,x2,y2);
    length+=calc(x1,y1,x3,y3);
    length+=calc(x2,y2,x3,y3);
    cout<<fixed<<setprecision(2)<<length;
    return 0;
}

加了abs也不行