#include <Servo.h>
// Nano: chap/o‘ng panja D3/D5, chap/o‘ng son D6/D9.
// HC-SR04: TRIG D7, ECHO D8. Servo quvvati tashqi, GND umumiy.
Servo joint[4];
const byte pins[] = {3,5,6,9};
void setup() {
  pinMode(7,OUTPUT); pinMode(8,INPUT);
  for (byte i=0;i<4;i++) { joint[i].attach(pins[i]); joint[i].write(90); }
}
void loop() {
  digitalWrite(7,LOW); delayMicroseconds(2);
  digitalWrite(7,HIGH); delayMicroseconds(10); digitalWrite(7,LOW);
  unsigned long echo=pulseIn(8,HIGH,25000);
  bool visitor=echo>=290 && echo<1740;
  int lean=visitor ? 6 : 0;
  joint[0].write(90+lean); joint[1].write(90-lean);
  joint[2].write(90-lean); joint[3].write(90+lean);
  delay(100);
}