..cpp

#include <bits/stdc++.h>
using namespace std;

// Macros and constants
#define endl ("\n")
#define pi (3.141592653589)
#define int long long
#define float double
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define all(c) c.begin(), c.end()
#define mini(a, b, c) min(c, min(a, b))
#define mini2(a, b, c, d) min(d, min(c, min(a, b))) 
#define rrep(i,s,n) for(int i=n-1;i>=s;i--)
#define rep(i,n) for(int i=0;i<n;i++)
#define fast ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
#define scin(str) getline(cin, str)

// Debugging Macros
#define debug(x) cerr << #x << " = " << x << endl
#define debug2(x, y) cerr << #x << " = " << x << ", " << #y << " = " << y << endl

// Aliases and Types
using vec = vector<int>;
using pii=pair<int,int>;
using mapi=map<int,int>;
using si=set<int>;

const int mod = 1e9+7;

// Global Constants
const int dx[4]{1, 0, -1, 0}, dy[4]{0, 1, 0, -1};  // for every grid problem!!
const int N=2e5+5;


int solution(vector<string> resources, int conversionRate) {
    long long countA = 0;
    long long countB = 0;

    for (const string& res : resources) {
        if (res == "a") {
            countA++;
        } else {
            countB++;
        }
    }

    int cycles = 0;
    while (true) {
        if (countB >= conversionRate) {
            // Option 1
            countB -= conversionRate;
            countA++;
            cycles++;
        } else if (countA > 0) {
            // Option 2
            countA--;
            countB++;
            cycles++;
        } else {
            // Option 3: Halt
            break;
        }
    }
    return cycles;
}

void solve(){
    int n;
    cin >> n;
    vector<string> arr(n);
    for(int i = 0; i < n; i++) cin >> arr[i];
    int r;
    cin >> r;
    int ans = solution(arr, r);
    cout << ans;
    
}


int32_t main(){
    fast

    int t = 1;
    // cin >> t;
    while(t--){
        
        
        solve();


    }
    return 0;
}