#include <bits/stdc++.h>
using namespace std;
const int N = 10010;
int a[N];  
int st[N]; 
int n, w;

int main() {
    cin >> n;
    for (int i = 1; i <= n; i++) cin >> a[i];
    cin >> w;
    if (n % w) {
        cout << "false" << endl;
        return 0;
    }
    sort(a + 1, a + 1 + n); 
    for (int i = 1; i <= n; i++) {
        if (!st[i]) {
            st[i] = 1;             
            int start = i + 1;     
            int target = a[i] + 1; 
            for (int j = 1; j < w; j++) {
                bool flag = false;
                for (int k = start; k <= n; k++) {
                    if (!st[k] && a[k] == target) {
                        st[k] = 1;
                        flag = true;
                        start = k + 1;
                        target++;
                        break;
                    }
                }
                if (!flag) {
                    cout << "false" << endl;
                    return 0;
                }
            }
        }
    }
    cout << "true" << endl;
    return 0;
}