Language: Java

import java.io.*;
import java.util.*;
import java.util.ArrayList;
 
class Main
{
  public static void main (String[] arg)
  {
    Scanner scan = new Scanner(System.in);
    
    int a = Integer.parseInt(scan.next()); //a
    
    if(a = 1){
      System.out.println("a");
    }
    else if(a = 2){
      System.out.println("aa");
      System.out.println("ab");
    }
    else if(a = 3){
      System.out.println("aaa");
      System.out.println("aab");
      System.out.println("aba");
    }
    else if(a = 4){
      System.out.println("aaaa");
      System.out.println("aaab");
      System.out.println("aaba");
      System.out.println("abaa");
    }
    else if(a = 5){
      System.out.println("aaaaa");
      System.out.println("aaaab");
      System.out.println("aaaba");
      System.out.println("aabaa");
      System.out.println("abaaa");
    }
     else if(a = 6){
      System.out.println("aaaaaa");
      System.out.println("aaaaab");
      System.out.println("aaaaba");
      System.out.println("aaabaa");
      System.out.println("aabaaa");
      System.out.println("abaaaa");
    }
    else if(a = 7){
      System.out.println("aaaaaaa");
      System.out.println("aaaaaab");
      System.out.println("aaaaaba");
      System.out.println("aaaabaa");
      System.out.println("aaabaaa");
      System.out.println("aabaaaa");
      System.out.println("abaaaaa");
    }
     else if(a = 8){
      System.out.println("aaaaaaaa");
      System.out.println("aaaaaaab");
      System.out.println("aaaaaaba");
      System.out.println("aaaaabaa");
      System.out.println("aaaabaaa");
      System.out.println("aaabaaaa");
      System.out.println("aabaaaaa");
      System.out.println("abaaaaaa");
    }
    else if(a = 9){
      System.out.println("aaaaaaaaa");
      System.out.println("aaaaaaaab");
      System.out.println("aaaaaaaba");
      System.out.println("aaaaaabaa");
      System.out.println("aaaaabaaa");
      System.out.println("aaaabaaaa");
      System.out.println("aaabaaaaa");
      System.out.println("aabaaaaaa");
      System.out.println("abaaaaaaa");
    }
    else if(a = 10){
      System.out.println("aaaaaaaaaa");
      System.out.println("aaaaaaaaab");
      System.out.println("aaaaaaaaba");
      System.out.println("aaaaaaabaa");
      System.out.println("aaaaaabaaa");
      System.out.println("aaaaabaaaa");
      System.out.println("aaaabaaaaa");
      System.out.println("aaabaaaaaa");
      System.out.println("aabaaaaaaa");
      System.out.println("abaaaaaaaa");
    }
  }
}

Compiler output:
Main.java:13: error: incompatible types: int cannot be converted to boolean
    if(a = 1){
         ^
Main.java:16: error: incompatible types: int cannot be converted to boolean
    else if(a = 2){
              ^
Main.java:20: error: incompatible types: int cannot be converted to boolean
    else if(a = 3){
              ^
Main.java:25: error: incompatible types: int cannot be converted to boolean
    else if(a = 4){
              ^
Main.java:31: error: incompatible types: int cannot be converted to boolean
    else if(a = 5){
              ^
Main.java:38: error: incompatible types: int cannot be converted to boolean
     else if(a = 6){
               ^
Main.java:46: error: incompatible types: int cannot be converted to boolean
    else if(a = 7){
              ^
Main.java:55: error: incompatible types: int cannot be converted to boolean
     else if(a = 8){
               ^
Main.java:65: error: incompatible types: int cannot be converted to boolean
    else if(a = 9){
              ^
Main.java:76: error: incompatible types: int cannot be converted to boolean
    else if(a = 10){
              ^
10 errors