#include <Keypad.h>

char keyPins[4][4] = {
  {'7','8','9','*'},
  {'4','5','6','-'},
  {'1','2','3','+'},
  {'0','.','=','C'}
};

byte rowPins[] = {13,12,14,27};
byte colPins[] = {26,25,33,32};

Keypad kp = Keypad(makeKeymap(keyPins), rowPins, colPins, 4, 4);

void setup() {
  Serial.begin(9600);
}

void loop() {
  char myKey = kp.getKey();

  if(myKey == keyPins[0][0]){
    Serial.println("Zmackol si 7");
  }
}