package problem;

import java.util.Stack;

public class EnglishFluent {
 public int simple (String s) {
 if (s.charAt(0) == '-') {
 s = '0' + s;
 }
 int num = 0;
 Stack<Integer> digitStack = new Stack<>();
 Stack<Character> opStack = new Stack<>();
 char[] c = s.toCharArray();
 for (int i = 0; i < c.length; i++) {
 if (Character.isDigit(c[i])) {
 num = num * 10 + c[i] - '0';
 } else {
 digitStack.push(num);
 num = 0;
 opStack.push(c[i]);
 }
 }
 digitStack.push(num);
 while (!opStack.isEmpty()) {
 int a = digitStack.pop();
 int b = digitStack.pop();
 char op = opStack.pop();
 if (opStack.isEmpty()) {
 if (op == '+') return a + b;
 else return b - a;
 } else if (opStack.peek() == '-') {
 if (op == '+') digitStack.push(b - a);
 else digitStack.push(b + a);
 } else {
 if (op == '+') digitStack.push(b + a);
 else digitStack.push(b - a);
 }
 }
 return 0;
 }
}