#include <bits/stdc++.h>
using namespace std;
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long n, t;
  cin >> n >> t;
  string str;
  cin >> str;
  long long ptr = 0;
  while (str[ptr] != '.') ptr++;
  long long tmp = ptr;
  ptr++;
  while (ptr < n and str[ptr] < '5') ptr++;
  if (ptr == n) {
    cout << str << "\n";
    return 0;
  }
  while (t) {
    if (str[ptr] < '5') {
      break;
    }
    if (str[ptr] >= '5') {
      str[ptr] = '\0';
      if (str[ptr - 1] != '.') {
        str[ptr - 1] = str[ptr - 1] + 1;
        t--;
        ptr--;
      } else {
        str[ptr - 1] = '\0';
        if (str[ptr - 2] == '9') {
          ptr = ptr - 2;
          while (ptr >= 0 and str[ptr] == '9') str[ptr--] = '0';
          if (ptr == -1) {
            cout << "1" << str.substr(0, tmp) << "\n";
            return 0;
          }
          str[ptr] = str[ptr] + 1;
          cout << str.substr(0, tmp) << "\n";
          return 0;
        }
        str[ptr - 2] += 1;
        cout << str.substr(0, tmp) << "\n";
        return 0;
      }
    }
  }
  long long len = 0;
  while (str[len] != '\0') len++;
  cout << str.substr(0, len) << "\n";
}
