import java.util.Stack;
import java.util.regex.Pattern;
public class StringToArithmetic {
    public StringToArithmetic() {
    }
    public static String stringToArithmetic(String string) {return suffixToArithmetic(infixToSuffix(string));}
    public static String infixToSuffix(String exp) {
        Stack<Character> s = new Stack<Character>();
        String suffix = "";
        int length = exp.length();
        for (int i = 0; i < length; i++) {
            char temp;
            char ch = exp.charAt(i);
            switch (ch) {
                case ' ':
                    break;
                case '(':
                    s.push(ch);
                    break;
                case '+':
                case '-':
                    while (s.size() != 0) {
                        temp = s.pop();
                        if (temp == '(') {
                            s.push('(');
                            break;
                        }
                        suffix += temp;
                    }
                    s.push(ch);
                    break;
                case '*':
                case '/':
                    while (s.size() != 0) {
                        temp = s.pop();
                        if (temp == '+' || temp == '-' || temp == '(') {
                            s.push(temp);
                            break;
                        } else {
                            suffix += temp;
                        }
                    }
                    s.push(ch);
                    break;
                case ')':
                    while (!s.isEmpty()) {
                        temp = s.pop();
                        if (temp == '(') {
                            break;
                        } else {
                            suffix += temp;
                        }
                    }
                    break;
                default:
                    suffix += ch;
                    break;
            }
        }
        while (s.size() != 0) {
            suffix += s.pop();
        }
        return suffix;
    }
    public static String suffixToArithmetic(String exp) {
        Pattern pattern = Pattern.compile("\\d+||(\\d+\\.\\d+)");
        String[] strings = exp.split("");
        Stack<Double> stack = new Stack<Double>();
        for (int i = 0; i < strings.length; i++) {
            if (strings[i].equals("")) {
                continue;
            }
            if (pattern.matcher(strings[i]).matches()) {
                stack.push(Double.parseDouble(strings[i]));
            }
            else {
                double y = stack.pop();
                double x = stack.pop();
                stack.push(calculate(x, y, strings[i]));
            }
        }
        return String.valueOf(stack.pop());
    }
    private static Double calculate(double x, double y, String string) {
        if (string.trim().equals("+")) {
            return x + y;
        }
        if (string.trim().equals("-")) {
            return x - y;
        }
        if (string.trim().equals("*")) {
            return x * y;
        }
        if (string.trim().equals("/")) {
            return x / y;
        }
        return (double) 0;
    }
}