#include<LiquidCrystal.h>
int rs = 7;
int en = 8;
int d4 = 9;
int d5 = 10;
int d6 = 11;
int d7 = 12;
int d = 1000;
String msg1 = "Enter first num: ";
String msg2 = "Enter second num: ";
String msg3 = "Enter operator: ";
float firstnum;
float secondnum;
float ans;
String op;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);
void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  lcd.begin(16, 2);
}

void loop() {
  // put your main code here, to run repeatedly:
  lcd.setCursor(0, 0);
  lcd.print(msg1);
  while (Serial.available() == 0) {}
  firstnum = Serial.parseFloat();
  Serial.find('\n'); // skip the remaining characters until end of line
  lcd.clear();
  lcd.setCursor(0, 0);

  lcd.print(msg2);
  while (Serial.available() == 0) {}
  secondnum = Serial.parseFloat();
  Serial.find('\n'); // skip the remaining characters until end of line  
  lcd.clear();
  lcd.setCursor(0, 0);

  lcd.print("Input operator(+,-,*,/)");
  while (Serial.available() == 0) {}
  op = (char)Serial.read();
  Serial.find('\n'); // skip the remaining characters until end of line

  if (op == "+")
  {
    ans = firstnum + secondnum;
  }
  if (op == "-")
  {
    ans = firstnum - secondnum;
  }
  if (op == "*")
  {
    ans = firstnum * secondnum;
  }
  if (op == "/")
  {
    ans = firstnum / secondnum;
  }
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print(firstnum);
  lcd.print(op);
  lcd.print(secondnum);
  lcd.print("=");
  lcd.print(ans);
  delay(2000);
}