#include <bits/stdc++.h>

 using namespace std;

 const long long INF = ;

 double dis(double x1, double y1, double x2, double y2)

 {

     return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));

 }

 int main()

 {

     int a, b, c;

     double x1, x2, y1, y2;

     while (cin >> a >> b >> c)

     {

         cin >> x1 >> y1 >> x2 >> y2;

         if (a ==  || b == )

         {

             printf("%.10f\n", fabs(x1 - x2) + fabs(y1 - y2));

             continue;

         }

         double n1 = x1, m1 = y2; // y1--y2

         double ty = (-a * x1 - c) / b;

         double tx = (-b * y2 - c) / a;

         double ans = fabs(x1 - x2) + fabs(y1 - y2);

         if (ty >= min(y1, y2) && ty <= max(y1, y2) && tx >= min(x1, x2) && tx <= max(x1, x2))

         {

             double tmp = fabs(y1 - ty) + fabs(x2 - tx) + dis(x1, ty, tx, y2);

             ans = min(ans, tmp);

         }

         double ty2 = (-a * x2 - c) / b;

         if (ty >= min(y1, y2) && ty <= max(y1, y2) && ty2 >= min(y1, y2) && ty2 <= max(y1, y2))

         {

             double tmp = fabs(y1 - ty) + fabs(ty2 - y2) + dis(x1, ty, x2, ty2);

             ans = min(ans, tmp);

         }

         double n2 = x2, m2 = y1; // x1--x2

         tx = (-b * y1 - c) / a;

         ty = (-a * x2 - c) / b;

         if (ty >= min(y1, y2) && ty <= max(y1, y2) && tx >= min(x1, x2) && tx <= max(x1, x2))

         {

             double tmp = fabs(x1 - tx) + fabs(y2 - ty) + dis(tx, y1, x2, ty);

             ans = min(ans, tmp);

         }

         double tx2 = (-b * y2 - c) / a;

         if (tx >= min(x1, x2) && tx <= max(x1, x2) && tx2 >= min(x1, x2) && tx2 <= max(x1, x2))

         {

             double tmp = fabs(x1 - tx) + fabs(tx2 - x2) + dis(tx, y1, tx2, y2);

             ans = min(ans, tmp);

         }

         printf("%.10f\n", ans);

     }

     return ;

 }