#include <iostream>
#include <stack>
#include <string>
using namespace std;
stack<long long> st;
string s;
int main()
{
    long long sum = 0;
    cin >> s;
    for (int i = 0; i < s.size(); i++)
    {
        long long a, b;
        if (s[i] == '.') continue;
        if (s[i] == '@')
        {
            cout << st.top();
            return 0;
        }
        if (s[i] == '+' || s[i] == '-' || s[i] == '*' || s[i] == '/')
        {
            a = st.top();
            st.pop();
            b = st.top();
            st.pop();
            if (s[i] == '+') st.push(a + b);
            if (s[i] == '-') st.push(b - a);
            if (s[i] == '*') st.push(a * b);
            if (s[i] == '/') st.push(b / a);
            continue;
        }
        st.push(s[i] - '0');
    }
}