slonopotam

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <random>
#include <set>
#include <iomanip>
using namespace std;
const int N = 5e5 + 7;
const long long INF = -1;
const long double eps = 1e-9;
struct vect {
    long double x, y;
};

vect operator+(vect a, vect b)
{
    return { a.x + b.x, a.y + b.y };
}
vect operator-(vect& a, vect& b)
{
    return { a.x - b.x, a.y - b.y };
}
vect operator*(vect& a, long double x)
{
    return { a.x * x, a.y * x };
}
vect operator/(vect& a, long double x)
{
    return { a.x / x, a.y / x };
}

long double operator %(const vect& a, const vect& b) { // vect
    return a.x * b.y - a.y * b.x;
}

long double operator *(const vect& a, const vect& b) { // skal
    return a.x * b.x + a.y * b.y;
}

bool operator==(vect& a, vect& b)
{
    return abs(a.x - b.x) < eps && abs(b.y - a.y) < eps;
}
long double len(vect a)
{
    return sqrtl(a.x * a.x + a.y * a.y);
}
vect norm(vect a, long double x)
{
    long double l = len(a);
    a = a / l;
    a = a * x;
    return a;
}
vect perp(vect a)
{
    return { a.y * -1, a.x };
}
vector<vect> PerOkr(vect o1, long double r1, vect o2, long double r2)
{
    vector<vect> ans;
    ans.clear();
    vect o2o1 = o1 - o2;
    long double z = len(o2o1);
    if (abs(r1 - r2) < eps && o1 == o2) {
        ans.push_back({ 1, 1 });
        ans.push_back({ 2, 2 });
        ans.push_back({ 3, 3 });
        return ans;
    }
    if (abs(z - r1 - r2) < eps) {
        ans.push_back(o2 + norm(o2o1, r2));
        return ans;
    }
    if (z > r1 + r2 + eps) { //
        return ans;
    }
    if (abs(z + r1 - r2) < eps) { // z == r1+r2, vnutr kas
        ans.push_back(o2 + norm(o2o1, r2));
        return ans;
    }
    if (abs(z + r2 - r1) < eps) { // z + r2 == r1, vnutr kas
        ans.push_back(o1 + norm(o2o1 * -1, r1));
        return ans;
    }
    if (z + r2 < r1 + eps || z + r1 < r2 + eps) { // odin vnutri drugogo
        return ans;
    }
    long double x = (z - (r1 * r1 - r2 * r2) / z) / 2;
    long double y = sqrtl(r2 * r2 - x * x);
    vect h = o2 + norm(o2o1, x);
    vect per = norm(perp(o2o1), y);
    cout << fixed << setprecision(10);
    vect o1h = h - o1;
    ans.push_back(h + per);
    ans.push_back(h - per);
    return ans;
}

vector<vect> Kas(vect o1, long double r1, vect o2) {
    vector<vect> ans;
    vect o2o1 = o1 - o2;
    long double z = len(o2o1);
    if (z < r1 - eps) {
        return ans;
    }
    if (abs(z - r1) < eps) {
        ans.push_back(o2);
        return ans;
    }
    long double r2 = sqrtl(z * z - r1 * r1);
    return PerOkr(o1, r1, o2, r2);
}

vect Intersect(vect a, vect b, vect c, vect d) {
    long double a1 = b.y - a.y;
    long double b1 = a.x - b.x;
    long double c1 = -1 * (a1 * a.x + b1 * a.y);
    long double a2 = d.y - c.y;
    long double b2 = c.x - d.x;
    long double c2 = -1 * (a1 * c.x + b1 * c.y);
    long double D = a1 * b2 - a2 * b1;
    long double Dx = c1 * b2 - c2 * b1;
    long double Dy = a1 * c2 - a2 * c1;
    if (D == 0) {
        return { -1337, -1448 };
    }
    return { -1 * (Dx / D), -1 * (Dy / D) };
}

long double RasstDoOtr(vect a, vect b, vect c) {
    vect ca = a - c;
    vect cb = b - c;
    vect bc = c - b;
    vect ba = a - b;
    vect ac = c - a;
    vect ab = b - a;
    if (ab * ac <= 0 || ba * bc <= 0) {
        return min(len(ac), len(bc));
    }
    return abs((ca % cb) / len(ab));
}

bool intC(vect o, long double r, vect a, vect b) {
    return RasstDoOtr(a, b, o) <= r + eps;
}
vect o, v, k;
long double r1, r2, n, ans;
vector<vect> ans1, ans2;
int main()
{
    cin >> v.x >> v.y >> k.x >> k.y >> o.x >> o.y >> r1;
    cout << fixed << setprecision(10);
    if (!intC(o, r1, v, k)) {
        cout << len(k - v);
        return 0;
    }
    ans1 = Kas(o, r1, v);
    ans2 = Kas(o, r1, k);
    ans = 1e12;
    for (int i = 0; i < ans1.size(); i++) {
        for (int j = 0; j < ans2.size(); j++) {
            vect oi = ans1[i] - o;
            vect oj = ans2[j] - o;
            //long double sect = min(abs(atan2(oi % oj, oi * oj)) * r1, 2 * acos(-1) * r1 - abs(atan2(oi % oj, oi * oj)) * r1);
            long double sect = abs(atan2(oi % oj, oi * oj)) * r1;
            ans = min(ans, len(v - ans1[i]) + len(k - ans2[j]) + sect);
        }
    }
    cout << ans;
}