#include <bits/stdc++.h>
using namespace std;
const int INF = 0x3f3f3f3f;
const long long LL_INF = 0x3f3f3f3f3f3f3f3f;
const int xx[4] = {1, -1, 0, 0};
const int yy[4] = {0, 0, 1, -1};
int inline in() {
  int x = 0, c;
  for (; (unsigned)((c = getchar()) - '0') >= 10;) {
    if (c == '-') return -in();
    if (!~c) throw ~0;
  }
  do {
    x = (x << 3) + (x << 1) + (c - '0');
  } while ((unsigned)((c = getchar()) - '0') < 10);
  return x;
}
int main() {
  cin.sync_with_stdio(false);
  cin.tie(0);
  int n, t;
  string buf;
  cin >> n >> t >> buf;
  int i = buf.find('.') + 1;
  while (i < n && buf[i] < '5') i++;
  if (i == n) {
    cout << buf << endl;
    return 0;
  }
  while (t-- && buf[i] >= '5') {
    i--;
    bool flag = (buf[i] == '.');
    if (flag) i--;
    buf[i]++;
    if (flag) break;
  }
  int len = i + 1;
  for (; i >= 1 && buf[i] == '9' + 1; i--) {
    buf[i] = '0';
    buf[i - 1]++;
  }
  if (buf[0] == '9' + 1) {
    buf[0] = '0';
    buf = '1' + buf;
    len++;
  }
  buf.resize(len);
  cout << buf << endl;
  return 0;
}
