#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <vector>

int N;
int d[100010];
int main() {
    scanf("%d", &N);
    std::vector<int> even, odd;
    for(int i=0; i<N; i++) {
        int p; scanf("%d", &p);
        (p%2 ? odd : even).push_back(p);
        d[i] = p;
    }

    int x, y; scanf("%d%d", &x, &y);

    // ans = 0
    if(x == 0 && y == 0) printf("0\n");
    else {
        // ans = 1
        int mh = abs(x) + abs(y);
        for(int i=0; i<N; i++) {
            if(mh == d[i]) {
                printf("1\n");
                return 0;
            }
        }

        // ans = 2
        std::sort(odd.begin(), odd.end());
        std::sort(even.begin(), even.end());
        std::sort(d, d+N);
        int ma = std::max(abs(x+y), abs(x-y));
        for(int i=0; i<N; i++) {
            int flr = abs(ma - d[i]);

            if(flr % 2) {
                // odd
                size_t idx = std::lower_bound(odd.begin(), odd.end(), flr) - odd.begin();
                if(idx != odd.size() && odd[idx] >= flr && odd[idx] < d[i]) {
                    printf("2\n");
                    return 0;
                } 
            }
            else {
                // even
                size_t idx = std::lower_bound(even.begin(), even.end(), flr) - even.begin();
                if(idx != even.size() && even[idx] >= flr && even[idx] < d[i]) {
                    printf("2\n");
                    return 0;
                }
            }
        }

        // no solution
        printf("-1\n");
    }
    return 0;
}