#define MAX_STACK_SIZE 20 

long valuesStack[MAX_STACK_SIZE];  
char operatorsStack[MAX_STACK_SIZE]; 
int valuesTop = -1;  
int operatorsTop = -1;  

void pushValue(long value) {
  if (valuesTop < MAX_STACK_SIZE - 1) {
    valuesStack[++valuesTop] = value;
  }
}

long popValue() {
  if (valuesTop >= 0) {
    return valuesStack[valuesTop--];
  }
  return 0;
}

void pushOperator(char op) {
  if (operatorsTop < MAX_STACK_SIZE - 1) {
    operatorsStack[++operatorsTop] = op;
  }
}

char popOperator() {
  if (operatorsTop >= 0) {
    return operatorsStack[operatorsTop--];
  }
  return 0;
}

char peekOperator() {
  if (operatorsTop >= 0) {
    return operatorsStack[operatorsTop];
  }
  return 0;
}

bool isOperatorsEmpty() {
  return operatorsTop == -1;
}

long calculate(long a, long b, char op) {
  switch (op) {
    case '+': return a + b;
    case '-': return a - b;
    case '*': return a * b;
    case '/': return (b != 0) ? (a / b) : 0; 
    default: return 0;
  }
}

int getPriority(char op) {
  if (op == '+' || op == '-') return 1;
  if (op == '*' || op == '/') return 2;
  return 0;
}

void processOperator(char op) {
  while (!isOperatorsEmpty() && getPriority(peekOperator()) >= getPriority(op)) {
    char oper = popOperator();
    long b = popValue();
    long a = popValue();
    pushValue(calculate(a, b, oper));
  }
  pushOperator(op);
}

long evaluateExpression(String expression) {
  for (int i = 0; i < expression.length(); i++) {
    char c = expression[i];

    if (isdigit(c)) {
      long num = 0; 
      while (i < expression.length() && isdigit(expression[i])) {
        num = num * 10 + (expression[i] - '0');
        i++;
      }
      i--; 
      pushValue(num);
    }
    else if (c == '(') {
      pushOperator(c);
    }
    else if (c == ')') {
      while (!isOperatorsEmpty() && peekOperator() != '(') {
        char oper = popOperator();
        long b = popValue();
        long a = popValue();
        pushValue(calculate(a, b, oper));
      }
      popOperator(); 
    }
    else if (c == '+' || c == '-' || c == '*' || c == '/') {
      processOperator(c);
    }
  }

  while (!isOperatorsEmpty()) {
    char oper = popOperator();
    long b = popValue();
    long a = popValue();
    pushValue(calculate(a, b, oper));
  }

  if (valuesTop >= 0) {
    return popValue();
  }

  return 0; 
}

void setup() {
  Serial.begin(9600);
  Serial.println("Введите арифметическое выражение:");
}

void loop() {
  if (Serial.available() > 0) {
    String expression = Serial.readStringUntil('\n');
    long result = evaluateExpression(expression); 
    Serial.print("Результат: ");
    Serial.println(result);
  }
}