#include<bits/stdc++.h>
#define fi first
#define se second
#define pb push_back
#define pf push_front
#define popb pop_back
#define popf pop_front
#define ins insert
#define pq priority_queue
#define minele min_element
#define maxele max_element
#define lb lower_bound //first pos >= val
#define ub upper_bound // first pos > val
#define cnt_bit __builtin_popcount
#define debug(...) " [" << #__VA_ARGS__ ": " << (__VA_ARGS__) << "] "
//#pragma GCC optimize("Ofast")
//#pragma GCC target("avx,avx2,fma")
using namespace std;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

typedef long long ll;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;


int d4x[4] = {1, 0, -1, 0}; int d4y[4] = {0, 1, 0, -1};
int d8x[8] = {0, 1, 1, 1, 0, -1, -1, -1};
int d8y[8] = {1, 1, 0, -1, -1, -1, 0, 1};

const ll oo = 1e18;
const ll maxN = 1e6;

/* Author : Le Ngoc Bao Anh, 10A5, LQD High School for Gifted Student */

void maximize(int &a, int b) {
    a = max(a, b);
}

void minimize(int &a, int b) {
    a = min(a, b);
}

int p[50], a[5], b[5];
int dp[1010][1010];
int f[22][(1 << 16)];

void solve() {
    int v, n, m;
    cin >> v >> n >> m;
    for(int i = 1; i <= n; i++) cin >> p[i];
    if(v <= 1000) {
        for(int i = 0; i <= v; i++) {
            for(int j = 0; j <= v; j++) {
                dp[i][j] = -1;
            }
        }
        dp[v][0] = 0;

        queue<pii> q;
        q.push(make_pair(v, 0));
        while(!q.empty()) {
            a[0] = q.front().fi, a[1] = q.front().se; q.pop();
            a[2] = v - a[0] - a[1];
            for(int i = 0; i <= 2; i++) {
                for(int j = 0; j <= 2; j++) {
                    if(i == j) continue;
                    //from ai to aj
                    for(int x = 0; x <= n; x++) {
                        if(a[i] <= p[x]) break;
                        int add = a[i] - p[x];
                        for(int y = 0; y < 3; y++) b[y] = a[y];
                        b[i] = a[i] - add; b[j] = a[j] + add;
                        if(dp[b[0]][b[1]] == -1) {
                            dp[b[0]][b[1]] = dp[a[0]][a[1]] + 1;
                            q.push(make_pair(b[0], b[1]));
                        }
                    }

                    for(int x = 0; x <= n; x++) {
                        if(a[j] >= p[x]) continue;
                        int add = p[x] - a[j];
                        if(add > a[i]) break;
                        for(int y = 0; y < 3; y++) b[y] = a[y];
                        b[i] = a[i] - add; b[j] = a[j] + add;
                        if(dp[b[0]][b[1]] == -1) {
                            dp[b[0]][b[1]] = dp[a[0]][a[1]] + 1;
                            q.push(make_pair(b[0], b[1]));
                        }
                    }
                }
            }
        }

        int ans = 1e9;
        for(int i = 0; i <= v; i++) {
            for(int j = 0; j <= v; j++) {
                if(dp[i][j] == -1) continue;
                if(i == m || j == m || (v - i - j) == m) ans = min(ans, dp[i][j]);
            }
        }

        if(ans == 1e9) ans = -1;
        cout << ans;
    } else {
        for(int i = 0; i <= n; i++) {
            for(int j = 0; j <= v; j++) f[i][j] = -1;
        }
        f[0][v] = 0;

        queue<pii> q;
        q.push(make_pair(0, v));
        while(!q.empty()) {
            int g = f[q.front().fi][q.front().se];
            a[0] = p[q.front().fi], a[1] = q.front().se; q.pop();
            a[2] = v - a[0] - a[1];
            for(int i = 0; i < 3; i++) {
                for(int j = 0; j < 3; j++) {
                    if(i == j) continue;

                    //from ai to aj
                    for(int x = 0; x <= n; x++) {
                        if(a[i] <= p[x]) continue;
                        int add = a[i] - p[x];
                        for(int y = 0; y < 3; y++) b[y] = a[y];
                        b[i] = p[x]; b[j] = a[j] + add;
                        if(f[x][b[j]] == -1) {
                            f[x][b[j]] = g + 1;
                            q.push(make_pair(x, b[j]));
                        }
                    }

                    for(int x = 0; x <= n; x++) {
                        if(a[j] >= p[x]) continue;
                        int add = p[x] - a[j];
                        if(add > a[i]) break;
                        for(int y = 0; y < 3; y++) b[y] = a[y];
                        b[i] = a[i] - add; b[j] = p[x];
                        if(f[x][b[i]] == -1) {
                            f[x][b[i]] = g + 1;
                            q.push(make_pair(x, b[i]));
                        }
                    }
                }
            }
        }

        int ans = 1e9;
        for(int i = 0; i <= n; i++) {
            for(int j = 0; j <= v; j++) {
                if(f[i][j] == -1) continue;
                if(p[i] == m || j == m || (v - p[i] - j == m)) ans = min(ans, f[i][j]);
            }
        }

        if(ans == 1e9) ans = -1;
        cout << ans;
    }
}

int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    #ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    #else
    //online
    #endif

    int tc = 1, ddd = 0;
    // cin >> tc;
    while(tc--) {
        //ddd++;
        //cout << "Case #" << ddd << ": ";
        solve();
    }
}