#include <bits/stdc++.h>
using namespace std;
int main() {
  long n, t;
  cin >> n >> t;
  string s1, s2;
  getline(cin, s1);
  getline(cin, s1, '.');
  getline(cin, s2);
  long a = -1, count = 0;
  for (int i = 0; i < s2.length(); i++)
    if (s2[i] >= '5') {
      a = i;
      break;
    }
  if (a == -1) {
    cout << s1 << '.' << s2;
    return 0;
  }
  if (a == 0) {
    int c = s1.length() - 1;
    while (s1[c] == '9' && c >= 0) c--;
    if (c == -1) {
      cout << '1';
      for (int i = 0; i < s1.length(); i++) cout << '0';
      return 0;
    }
    s1[c]++;
    for (c++; c < s1.length(); c++) s1[c] = '0';
    cout << s1;
    return 0;
  }
  long b = a - 1;
  while (s2[b] == '4' && b >= 0 && b >= a - t + 1) {
    b--;
  }
  if (b == -1) {
    int c = s1.length() - 1;
    while (s1[c] == '9' && c >= 0) c--;
    if (c == -1) {
      cout << '1';
      for (int i = 0; i < s1.length(); i++) cout << '0';
      return 0;
    }
    s1[c]++;
    for (c++; c < s1.length(); c++) s1[c] = '0';
    cout << s1;
    return 0;
  } else {
    s2[b]++;
    cout << s1 << '.';
    for (int i = 0; i <= b; i++) cout << s2[i];
    return 0;
  }
  return 0;
}
