#include <bits/stdc++.h>
using namespace std;
int N, Cnt = 0;
double A[4005], C[4005], Ans = 0.0, Anx;
double Abs(double x) { return x < 0 ? -x : x; }
int main() {
  scanf("%d", &N);
  for (int i = 1; i <= 2 * N; i++) scanf("%lf", &A[i]), C[i] = A[i] - (int)A[i];
  for (int i = 1; i <= 2 * N; i++) {
    if (C[i] == 0) Cnt++;
    Ans += -C[i];
  }
  Anx = Abs(Ans + 1.0 * N);
  for (int i = max(N - Cnt, 0); i <= N; i++) {
    Anx = min(Anx, Abs(Ans + i));
  }
  printf("%.3f\n", Anx);
  return 0;
}
