Question about c++ in arduino IDE

I am trying to split a string using a ", " as a delimiter.And then assign each integer to a variable:

For example:

Say you enter a string in this format: 1,2

Then the code will assign num1 = 1 and num2 = 2.

Please take a look at what I have. I can't find themistake.

int num1 = 0;
int num2 = 0;
char str[100];

int j = 0;

void setup() {
Serial.begin(9600);
Serial.print("Enter string in this format 1,2");
}

void loop() {
while (Serial.available() > 0)
{
j = 1;
}
if (j == 1)
{
char* point;
point = strtok(str, ",");
num1 = atoi(point);
point = strtok(NULL, ",");
num2 = atoi(point);

Serial.print("num1 = ");
Serial.println(num1);
Serial.print("num2 = ");
Serial.println(num2);
j = 0;
}
}