#include<bits/stdc++.h>
using namespace std;
const long long MaxN = 2e3 + 5;
long long n;
double x[MaxN], y[MaxN],dp[MaxN][MaxN];

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cin >> n;
    for (long long i=1; i<=n; i++)
    {
        cin >> x[i] >> y[i];
    }
    for (long long i=1; i<=n; i++)
    {
       for (long long j=1; j<=n; j++)
       {
           dp[i][j]=1e18;
       }
    }
    dp[1][1]=0;
    for (long long i=1; i<=n; i++)
    {
        for (long long j=1; j<=i; j++)
        {
            dp[i+1][j]=min(dp[i+1][j],dp[i][j]+sqrt((x[i]-x[i+1])*(x[i]-x[i+1])+(y[i]-y[i+1])*(y[i]-y[i+1])));
            dp[i+1][i]=min(dp[i+1][i],dp[i][j]+sqrt((x[j]-x[i+1])*(x[j]-x[i+1])+(y[j]-y[i+1])*(y[j]-y[i+1])));
        }
    }
    double ans = 4e18;
    for (long long i=1; i<=n; i++)
    {
        ans=min(ans,dp[n][i]);
    }
    cout << fixed <<  setprecision(10) << ans;
}