#include <bits/stdc++.h>   using namespace std;   int where[26][26];   int n, dp[(1 << 23) + 5], d[35];   bool fdp[(1 << 23) + 5];   int rec(int mask) {     if (fdp[mask]) return dp[mask];     int next = 0;     for (int i = n - 1; i >= 0; --i) {       if (mask & (1 << i)) {         next = i;         break;       }     }     next++;     fdp[mask] = 1;     if (next == n) return dp[mask] = __builtin_popcount(mask);     int make = d[next + 1];     dp[mask] = 30;     int valid = 0;     for (int i = 0; i < n; ++i) {       if (mask & (1 << i)) {         int j = where[next + 1][i + 1];         if (d[i + 1] < make and j) {           j--;           if (mask & (1 << j)) valid = 1;         }       }     }     if (valid) {       dp[mask] = rec(mask | (1 << next));       for (int i = 0; i < next; ++i) {         if (mask & (1 << i))           dp[mask] = min(dp[mask], rec((mask ^ (1 << i)) | (1 << next)));       }     }     return dp[mask];   }   int main() {     cin >> n;     for (int i = 1; i <= n; ++i) {       cin >> d[i];     }     for (int i = 1; i <= n; ++i) {       for (int j = 1; j <= n; ++j) {         int f = d[i] - d[j];         for (int k = 1; k <= n; ++k) {           if (d[k] == f) {             where[i][j] = k;           }         }       }     }     int ans = rec(1);     if (ans == 30) ans = -1;     cout << ans;   }   