I am receiving data from an LDR which I am inputting into processing. The data seems to be received to Arduino correctly however when I try to constrain and map the values into data processing can compute it prints a series of values with letters in front rather than values between the range I have specified. Any help identifying where I have gone wrong would be so so helpful!

ARDUINO CODE

int rval=0;
int lightval;

//Recorded minimum and maximum values
int minval=0;
int maxval=950;

void setup() 
{
  Serial.begin(9600); 
}

void loop() 
{
  rval = analogRead(1);
  Serial.println(rval);
  rval=constrain(rval,minval,maxval); //constrain the value rval between 0 and 950. 
  lightval=map(rval,minval,maxval,0,255); //converts the range of rval. Mapped from 0-950 to 0-255. now stored as lightval.
  Serial.println(lightval);
  Serial.write(lightval);
}