public boolean lemonadeChange(int[] bills) {

int fives = 0, tenners = 0, twenties = 0;

for (int i = 0 ; i < bills.length && fives >= 0 && tenners >= 0 && twenties >= 0 ; i++) {

if (bills[i] == 20) {

if (tenners > 0) {

tenners--;

fives--;

} else {

fives -= 3;

}

twenties++;

} else if (bills[i] == 10) {

fives--;

tenners++;

} else fives++;

}

return fives >=0 && tenners >= 0 && twenties >= 0;

}