int led1 = 10;
int led2 = 11;
int led3 = 12;
int sw1 = 1;
int sw2 = 2;
int sw3 = 3;
int sw4 = 4;

void setup() {
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  pinMode(led3, OUTPUT);

  pinMode(sw1, INPUT);
  pinMode(sw2, INPUT);
  pinMode(sw3, INPUT);
  pinMode(sw4, INPUT);
}

void loop() {

  if (digitalRead(sw1) == HIGH) {

    digitalWrite(led3, HIGH);
    digitalWrite(led2, LOW);
    digitalWrite(led1, LOW);
    delay(100);
  }
  if (digitalRead(sw2) == HIGH) {

    digitalWrite(led3, LOW);
    digitalWrite(led2, HIGH);
    digitalWrite(led1, LOW);
    delay(100);
  }
  if (digitalRead(sw3) == HIGH) {

    digitalWrite(led3, LOW);
    digitalWrite(led2, LOW);
    digitalWrite(led1, HIGH);
    delay(100);
  }
  if (digitalRead(sw4) == HIGH) {

    digitalWrite(led3, LOW);
    digitalWrite(led2, LOW);
    digitalWrite(led1, LOW);
    delay(100);
  }
}