#include <bits/stdc++.h>   using namespace std;   int n, arr[2005], counts[2005];   char c =  a ;   int main() {     cin >> n;     for (int i = 0; i < n; i++) {       cin >> arr[i];     }     for (int i = n - 1; i >= 0; i--) {       counts[i] = arr[i];       if (arr[i] != 0) {         for (int j = i - 1; j >= 0; j--) {           arr[j] -= (i - j + 1) * arr[i];         }       }     }     for (int i = 1; i <= n; i++) {       for (int j = 0; j < counts[i - 1]; j++) {         for (int k = 0; k < i; k++) {           cout << c;         }         c = ((c ==  a ) ?  b  :  a );       }     }   }   