const int R1=18,R2=5,R3=17,R4=16;
const int C1=4,C2=0, C3=2, C4=15;


void setup() {
  Serial.begin(115200);
pinMode(R1, OUTPUT);
pinMode(R2, OUTPUT);
pinMode(R3, OUTPUT);
pinMode(R4, OUTPUT);
pinMode(C1, INPUT_PULLUP);
pinMode(C2,  INPUT_PULLUP);
pinMode(C3,  INPUT_PULLUP);
pinMode(C4,  INPUT_PULLUP);
digitalWrite(C1, HIGH);
digitalWrite(C2, HIGH);
digitalWrite(C3, HIGH);
digitalWrite(C4, HIGH);

}
void loop() {
digitalWrite(R1, LOW);
digitalWrite(R2, LOW);
digitalWrite(R3, LOW);
digitalWrite(R4, LOW);
if (digitalRead(C1)==LOW) 
{
Serial.println("1");
delay(100);}
else if (digitalRead(C2)==LOW) {
Serial.println("2");
delay(100);}
else if (digitalRead(C3)==LOW) 
{Serial.println("3");
delay(100);}
else if(digitalRead(C4)==LOW) {
Serial.println("A");
delay(100);
}


}