Array.prototype.remove = function() {
    var what, a = arguments, L = a.length, ax;
    while (L && this.length) {
        what = a[--L];
        while ((ax = this.indexOf(what)) !== -1) {
            this.splice(ax, 1);
        }
    }
    return this;
};

let map =[]
const N = parseInt(readline());
let TotalDistance = 0
for (let i = 0; i < N; i++) {
    var inputs = readline().split(' ');
    const X = parseInt(inputs[0]);
    const Y = parseInt(inputs[1]);
    map.push([X,Y])
    }

let currentLoc = map[0]
for(let i = 0; i< map.length; i){
print(currentLoc)
print(map)
print(map.indexOf(currentLoc))
map.remove(currentLoc)

let CurrentDistance = 10000
let chosenLoc = [0,0]
for(let j = map.length-1; j>=0;j--){
let newDist = Math.sqrt(Math.pow(map[j][0]-currentLoc[0],2)+Math.pow(map[j][1]-currentLoc[1],2))


if(CurrentDistance>newDist){
    CurrentDistance=newDist
    chosenLoc = [map[j][0],map[j][1]]


}
}
TotalDistance += CurrentDistance

currentLoc[0] = chosenLoc[0]
currentLoc[1] = chosenLoc[1]

}

print(TotalDistance)