#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <queue>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;

static const double EPS = 1e-8;
static const double PI = 4.0 * atan(1.0);
static const double PI2 = 8.0 * atan(1.0);

#define REP(i,n)	for(int i=0;i<(int)n;++i)
#define ALL(c)		(c).begin(),(c).end()
#define CLEAR(v)	memset(v,0,sizeof(v))
#define MP(a,b)		make_pair((a),(b))
#define ABS(a)		((a)>0?(a):-(a))
#define FOR(i,s,n)	for(int i=s;i<(int)n;++i)

int N;
double X[1000], Y[1000];
int es[1000][1000];
int c[1000];

typedef pair<int, int> P;

int main(int argc, char **argv) {
	cin >> N;
	REP(i, N) cin >> X[i] >> Y[i];
	REP(i, N) es[i][i] = 1000000000;
	REP(i, N) FOR(j, i + 1, N) {
		double dx = X[j] - X[i], dy = Y[j] - Y[i];
		es[i][j] = (int)ceil(hypotl(dx, dy) / 10);
		es[j][i] = es[i][j];
	}
	REP(i, N) c[i] = 1000000000;
	priority_queue<P, vector<P>, greater<P>> q;
	q.push(MP(0, 0));
	while (!q.empty()) {
		P p = q.top(); q.pop();
		int f = p.first, v = p.second;
		if (c[v] <= f) continue;
		c[v] = f;
		if (v == N - 1) break;
		REP(i, N) {
			if (i == v) continue;
			q.push(MP(max(f, es[v][i]), i));
		}
	}
	cout << ((ll)10 * c[N - 1]) << endl;
	return 0;
}