issue with assignment operator inside printf()

Here is the code

int main()
{
  int x=15;
  printf("%d %d %d %d",x=1,x<20,x*1,x>10);
  return 0;
}

And output is 1 1 1 1

I was expecting 1 1 15 1 as output,

x*1 equals to 15 but here x*1 is 1 , Why ? Using assignment operator or modifying value inside printf() results in undefined behaviour?