class AccountA {
 private int amount;

 public AccountA() {
     amount = 0;
 }

 public AccountA(int sum) {
     amount=sum;
 }

 public void deposit(int sum) {
     amount+=sum;
 }

 public boolean withdraw(int sum) {
     if(sum<=amount) {
         amount-=sum;
         return true;
     }
     else return false;
 }

 public boolean transfer(AccountA acc,int sum) {
     if(sum<=amount) {
         amount-=sum;
         acc.amount+=sum;
         return true;
     }
     else return false;
 }

 public AccountA open(int sum) {
    if(sum<=amount) {
       amount-=sum;
       return new AccountA(sum);
    }
    else return null;
 }

 public int balance() {
    return amount;
 }
}