//keypad library is literally just "Keypad"

#include <Keypad.h>
#define led1 16
const byte ROWS = 4;
const byte COLS = 3;
char keys[ROWS][COLS]={
  {'1','2','3'},
  {'4','5','6'},
  {'7','8','9'},
  {'*','0','#'}
};
byte rowPins[ROWS]={17,18,19,5};
byte colPins[COLS]={21,22,23};
Keypad keypad=Keypad(makeKeymap(keys),rowPins,colPins,ROWS,COLS);


void setup() {
  pinMode(led1, OUTPUT);
  Serial.begin(115200);
}


void loop() {
  char key=keypad.getKey();
  if(key){ //if any key is pressed
    Serial.println(key);
    digitalWrite(led1,HIGH);
    delay(200);
    digitalWrite(led1,LOW);
  }
}