#include<iostream>
#include<cstring>
#include<vector>
#include<cmath>
#include<iomanip>
using namespace std;
using LL = long long;

int main(){

#ifdef LOCAL
    freopen("data.in", "r", stdin);
    freopen("data.out", "w", stdout);
#endif

    cin.tie(0);
    cout.tie(0);
    ios::sync_with_stdio(0);

    int x[3], y[3];
    for(int i = 0; i < 3; i++) cin >> x[i] >> y[i];
    double ans = 0;
    
    auto dist = [&](int a, int b){
        int dx = x[a] - x[b];
        int dy = y[a] - y[b];
        return sqrt(dx * dx + dy * dy);
    };

    for(int i = 0; i < 3; i++){
        ans += (i + 1) * dist(i, 2);
    }
    cout << fixed << setprecision(20) << ans << '\n';

}