#include <iostream>
#include <string>
#include <algorithm>
#include <vector>

using namespace std;

#define ull unsigned long long
#define p_b push_back

vector<ull> all;

ull to_int(string &s) {
    ull ans = 0;
    for (int i = 0; i < s.size(); i++) {
        ans = ans * 10 + (s[i] - '0');
    }
    return ans;
}

ull ip_to_int(string &s) {
    string l = "";
    ull ans = 0;
    for (int i = 0; i < s.size(); i++) {
        if (s[i] != '.')
            l += s[i];
        else {
            ans = ans * 256 + to_int(l);
            l = "";
        }
    }
    ans = ans * 256 + to_int(l);
    return ans;
}

int main()
{
    cin.tie(0);
    cout.tie(0);
    ios_base::sync_with_stdio(0);
    int n, x;
    cin >> n >> x;
    string s;
    for (int i = 0; i < n; i++) {
        cin >> s;
        all.p_b(ip_to_int(s));
    }
    cin >> s;
    ull a = ip_to_int(s);
    cin >> s;
    ull b = ip_to_int(s);
    ull in_deap = 0;
    bool a_in = 0, b_in = 0;
    for (int i = 0; i < all.size(); i++) {
        if (all[i] > a && all[i] < b)
            in_deap++;
        if (a == all[i])
            a_in = 1;
        if (b == all[i])
            b_in = 1;
    }
    if (!a_in)
        all.p_b(a);
    if (!b_in)
        all.p_b(b);
    sort(all.begin(), all.end());
    ull res = -1;
    for (int i = 0; i < all.size() - 1; i++) {
        if (all[i] >= a && all[i + 1] <= b && all[i + 1] - all[i] >= 2) {
            if (all[i] == a && !a_in) {
                if (res == -1)
                    res = b - a - b_in;
                else
                    res = min(b - a - b_in , res);
            }
            if (all[i + 1] == b && !b_in) {
                if (res == -1)
                    res = b - a - a_in;
                else
                    res = min(b - a - a_in, res);
            }
        }
        if (all[i + 1] - all[i] >= 3 && all[i] > a && all[i + 1] < b) {
            if (res == -1)
                res = b - a - a_in - b_in;
            else
                res = min(b - a - a_in - b_in, res);
        }
    }
    if (a + 1 == b && !a_in && !b_in) {
        cout << 0;
        return 0;
    }
    if (res != -1)
        cout << res - in_deap - 1;
    else
        cout << -1 << endl;
    return 0;
}