#include <bits/stdc++.h>   using namespace std;   void solve() {     long long n, k, kol = 0;     cin >> n >> k;     string s;     cin >> s;     vector<long long> a(n);     for (long long i = 0; i < n; i++) {       a[i] = s[i] -  0 ;     }     for (long long i = 0; i < n - 1 && k; i++) {       if (a[i] == 4 && a[i + 1] == 7) {         if (i % 2 == 0) {           a[i + 1] = 4;           k--;         } else {           if (i > 0 && a[i - 1] == 4) {             if (k % 2 == 1) {               a[i] = 7;             }             break;           }           a[i] = a[i + 1] = 7;           k--;         }       }     }     for (long long i = 0; i < n; i++) {       cout << a[i];     }   }   signed main() {     ios_base::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     long long t = 1;     while (t--) {       solve();     }   }   