int col1 = 2;
int col2 = 3;
int row1 = 4;
int row2 = 5;

void setup() {
pinMode(col1, OUTPUT);
pinMode(col2, OUTPUT);
pinMode(row1, INPUT_PULLUP);
pinMode(row2, INPUT_PULLUP);
Serial.begin(9600);
}

void loop() {
digitalWrite(col1, LOW);
digitalWrite(col2, HIGH);
if (digitalRead(row1) == LOW){
  Serial.println("1");
}
if (digitalRead(row2) == LOW){
  Serial.println("3");
}
digitalWrite(col1, HIGH);
digitalWrite(col2, LOW);
if (digitalRead(row1) == LOW){
  Serial.println("2");
}
if (digitalRead(row2) == LOW){
  Serial.println("4");
}

}