Solution

#include <bits/stdc++.h>
using namespace std;
string expr;
int getPriority(char c) {
    if (c == '(')
        return 1;
    if (c == ')')
        return 2;
    if (c == '+' || c == '-')
        return 3;
    if (c == '*' || c == '/')
        return 4;
    return -1;
}
string trans(string expr) {
    int len = expr.size() - 1;
    string ret = "";
    stack<char> op;
    bool flag = false;
    string num = "";
    for (int i = 0; i < len; ++i) {
        char c = expr[i];
        if (c >= '0' && c <= '9') {
            num += c;
            flag = true;
        }

        if (getPriority(c) != -1 && flag) {
            ret += num + " ";
            flag = false;
            num = "";
        }

        if (c == '(')
            op.push(c);
        else if (c == ')') {
            while (!op.empty() && op.top() != '(') {
                ret.push_back(op.top());
                op.pop();
            }
            if (op.empty()) {
                cout << "NO" << endl;
                exit(0);
            }
            op.pop();
        } else if (getPriority(c) != -1) {
            while (!op.empty() && getPriority(op.top()) >= getPriority(c)) {
                ret.push_back(op.top());
                op.pop();
            }
            op.push(c);
        }
    }
    if (flag)
        ret += num + " ";
    while (!op.empty()) {
        if (op.top() == '(') {
            cout << "NO" << endl;
            exit(0);
        }
        ret.push_back(op.top());
        op.pop();
    }
    return ret;
}
int main() {
    getline(cin, expr);
    expr = trans(expr);
    // cout << expr << endl;
    stack<int> val;

    int len = expr.size();
    for (int i = 0; i < len; ++i) {
        char c = expr[i];
        if (c == ' ')
            continue;
        if (c >= '0' && c <= '9') {
            int num = c - '0';
            while (expr[i + 1] != ' ') {
                i++;
                num = num * 10 + expr[i] - '0';
            }
            val.push(num);
        } else {
            if (val.size() < 2) {
                cout << "NO" << endl;
                return 0;
            }
            int y = val.top();
            val.pop();
            int x = val.top();
            val.pop();
            if (c == '*')
                val.push(x * y);
            else if (c == '/') {
                val.push(x / y);
            } else if (c == '+') {
                val.push(x + y);
            } else if (c == '-') {
                val.push(x - y);
            }
        }
    }
    if (val.size() >= 2)
        cout << "NO" << endl;
    else
        cout << val.top() << endl;
    return 0;
}