全部点都错了

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

struct zc {
    int x;
    int y;
}a[4];

int cd(zc a, zc b) {
    double a1 = pow((b.x - a.x), 2.0);
    double a2 = pow((b.y - a.y), 2.0);
    double zc = pow((a1 + a2), 1 / 2);
    return zc;
}

int main() {
    for (int i = 1; i <= 3; i++) {
        cin >> a[i].x >> a[i].y;
    }
    double zzc = cd(a[1], a[2]) + cd(a[1], a[3]) + cd(a[2], a[3]);
    printf("%0.2lf", zzc);
    return 0;
}

按公式写的