I don't have much experience in C++ programming. I'm getting this error

'z' does not name a type!!!

which I have't seen in MATLAB or python... What's wrong??? It is so simple!!!

float x=10; float y=50; float z;
z=x*y;

void setup() {
  // put your setup code here, to run once:
}

void loop() {
  // put your main code here, to run repeatedly:
}