#include <bits/stdc++.h>
using namespace std;
void ga(int N, int *A) {
  for (int i(0); i < N; i++) scanf("%d", A + i);
}
struct pt {
  double x, y;
  pt operator-(pt r) { return {x - r.x, y - r.y}; }
  pt operator+(pt r) { return {x + r.x, y + r.y}; }
  pt operator*(double a) { return {x * a, y * a}; }
  bool operator<(const pt &r) const {
    return (x + (1e-10) > r.x && x - (1e-10) < r.x) ? y < r.y : x < r.x;
  }
  bool operator==(const pt &r) const {
    return (x + (1e-10) > r.x && x - (1e-10) < r.x) &&
           (y + (1e-10) > r.y && y - (1e-10) < r.y);
  };
  double dst(pt r = {0, 0}) {
    return sqrt((x - r.x) * (x - r.x) + (y - r.y) * (y - r.y));
  }
  double XP(pt b) { return x * b.y - y * b.x; }
  double DT(pt &b) { return x * b.x + y * b.y; }
  bool gt() { return ~scanf("%lf%lf", &x, &y); }
  void prt() { printf("%.3lf %.3lf\n", x, y); }
} p[(2048)], P = {0, 0};
double XX(pt &a, pt &b, pt &c) {
  return (a.x - c.x) * (b.y - c.y) - (b.x - c.x) * (a.y - c.y);
}
bool cp(pt a, pt b) {
  return (a.y + (1e-10) > b.y && a.y - (1e-10) < b.y) ? a.x < b.x : a.y < b.y;
}
int N, A, B, S;
double T;
int main(void) {
  scanf("%d", &N);
  for (int i(0); i < N; i++) p[i].gt();
  for (int i(0); i < N; i++) P = P + p[i];
  T = P.y / N;
  printf("%.3lf\n", T + 5);
  return 0;
}
