#include <bits/stdc++.h>   using namespace std;   int main() {     int n;     cin >> n;     string s;     cin >> s;     int cnt = 0;     for (int i = 0; i < n; i += 2) {       if (s[i] == s[i + 1]) {         cnt++;         if (s[i] ==  a )           s[i] =  b ;         else           s[i] =  a ;       }     }     cout << cnt << endl << s;     return 0;   }   