phcbest

```kotlin
fun add(a: Int, b: Int): Int {
var carry: Int
var sum: Int
do {
sum = a xor b
carry = (a and b) shl 1
a = sum
b = carry
} while (b != 0)
return a
}

fun subtract(a: Int, b: Int): Int {
return add(a, add(b.inv(), 1))
}

fun multiply(a: Int, b: Int): Int {
var result = 0
var shift = 0
var bCopy = b
while (bCopy != 0) {
if (bCopy and 1 == 1) {
result = add(result, a shl shift)
}
shift++
bCopy = bCopy shr 1
}
return result
}

fun divide(a: Int, b: Int): Int {
var dividend = a
var divisor = b
var quotient = 0
while (dividend >= divisor) {
dividend = subtract(dividend, divisor)
quotient = add(quotient, 1)
}
return quotient
}
```