const int A = 3;
const int B = 5;
void setup() {
  pinMode(A, OUTPUT);
  pinMode(B, OUTPUT);

}

void loop() {
  for(int i=1;i<=255;i++)
  {
    int j =255-i;
    analogWrite(A,i);
    analogWrite(B,j);
    delay(100);
  }
  for(int i=255;i>0;i--)
  {
    int j =255-i;
    analogWrite(B,j);
    analogWrite(A,i);
    delay(100);
  }
}