#include <bits/stdc++.h>
using namespace std;
const double PI = 3.14159265359;
double ans, x, y;
int n, zeros, ones;
int main() {
  scanf("%d", &n);
  for (int i = 0; i < 2 * n; ++i) {
    scanf("%lf", &y);
    x -= y - int(y);
    if (y == int(y))
      ++zeros;
    else
      ++ones;
  }
  assert(zeros + ones == 2 * n);
  int i = 0;
  while (i < min(n, ones) && fabs(x) >= fabs(x + 1)) x += 1.0, ++i;
  while (i < n && zeros) ++i, --zeros;
  while (i < n) x += 1.0, ++i;
  printf("%.3lf", fabs(x));
  return 0;
}
