#include <iostream> 
#include <time.h> 
using namespace std; 
  
int main() 
{ 
    // for producing different random  
    // numbers every time. 
    srand(time(0)); 
  
    // random length of string from 1 - 16 
    // we are taking input from input stream, 
    // we can take delimiter to end the string 
    int max = 1 + rand() % 15; 
  
    // generating random string and processing it 
    int i = 0; 
    while (i < max) { 
  
        // producing random character over 
        // input alphabet (a, b) 
        char c = 'a' + rand() % 2; 
        cout << c << " "; 
        i++; 
  
        // first character is 'a' 
        if (c == 'a') { 
  
            // if there is only 1 character 
            // i.e. 'a' 
            if (i == max) 
                cout << "YES\n"; 
  
            while (i < max) { 
                c = 'a' + rand() % 2; 
                cout << c << " "; 
                i++; 
  
                // if character is 'a' and it 
                // is the last character 
                if (c == 'a' && i == max) { 
                    cout << "\nYES\n"; 
                } 
  
                // if character is 'b' and it  
                // is the last character 
                else if (i == max) { 
                    cout << "\nNO\n"; 
                } 
            } 
        } 
  
        // first character is 'b' so no matter 
        // what the string is, it is not going  
        // to be accepted 
        else { 
            while (i < max) { 
                c = 'a' + rand() % 2; 
                cout << c << " "; 
                i++; 
            } 
            cout << "\nNO\n"; 
        } 
    } 
  
    return 0; 
}