#include <bits/stdc++.h>   using namespace std;   const int maxN = 23;   const int mod = 1000 * 1000 * 1000 + 7;   int dp[2][1 << maxN];   int a[maxN];   int res[maxN][maxN];   int main() {     ios_base::sync_with_stdio(0);     cin.tie(0);     int n;     cin >> n;     for (int i = 0; i < n; i++) cin >> a[i];     dp[0][1] = 1;     dp[0][0] = mod;     memset(res, -1, sizeof res);     for (int i = 0; i < n; i++)       for (int j = 0; j < i; j++)         for (int k = 0; k < i; k++)           if (a[j] + a[k] == a[i]) res[i][j] = k;     for (int i = 1; i < n; i++) {       int u = i & 1;       for (int mask = 0; mask < (1 << (i + 1)); mask++) dp[u][mask] = mod;       for (int mask = 0; mask < (1 << i); mask++) {         for (int j = 0; j < i; j++) {           if (res[i][j] == -1) continue;           if (mask >> j & 1)             if (mask >> res[i][j] & 1) {               int tmp = mask ^ (1 << i);               dp[u][tmp] =                   min(dp[u][tmp], max(__builtin_popcount(tmp), dp[!u][mask]));               for (int k = 0; k < i; k++) {                 if (mask >> k & 1) {                   dp[u][tmp ^ (1 << k)] =                       min(dp[u][tmp ^ (1 << k)], dp[!u][mask]);                 }               }               break;             }         }       }     }     int ans = mod;     for (int mask = 0; mask < (1 << n); mask++)       ans = min(ans, dp[(n - 1) & 1][mask]);     if (ans == mod)       cout << -1 << endl;     else       cout << ans << endl;     return 0;   }   