#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, t;
  scanf("%d%d", &n, &t);
  string s;
  cin >> s;
  string s1 = "", s2 = "";
  bool ck = 0;
  for (int i = 0; i < s.size(); i++) {
    if (s[i] == '.')
      ck = 1;
    else if (ck)
      s2 += s[i];
    else
      s1 += s[i];
  }
  if (ck == 0) {
    cout << s << endl;
    return 0;
  }
  int cnt = 0;
  ck = 0;
  for (int i = 0; i < s2.size(); i++) {
    if (s2[i] >= '5') {
      cnt = i;
      ck = 1;
      break;
    }
  }
  int cp = 0;
  if (ck) {
    while (cnt >= 0) {
      if (cp == t) break;
      cp++;
      cnt--;
      int val = (s2[cnt] - '0') + 1;
      s2[cnt] = (val + '0');
      if (val < 5) break;
    }
    if (cnt == -1) {
      int len = s1.size();
      string sl = "";
      for (int i = 0; i < len - 1; i++) sl += '0';
      sl += "1";
      int ca = 0;
      string s9 = "";
      for (int i = len - 1; i >= 0; i--) {
        int val = (s1[i] - '0') + (sl[i] - '0') + ca;
        ca = val / 10;
        s9 += (val % 10 + '0');
      }
      if (ca) s9 += (ca + '0');
      reverse(s9.begin(), s9.end());
      cout << s9 << endl;
    } else {
      cout << s1 << ".";
      if (ck)
        for (int i = 0; i <= cnt; i++) cout << s2[i];
      else
        cout << s2 << endl;
      cout << endl;
    }
  } else {
    cout << s << endl;
  }
}
