include <fstream>
#include <stack>
#include <cctype>
using namespace std;

int main(){
    ifstream fin("postfix.in");
    ofstream fout("postfix.out");
    char symbol;
    stack<int> result;
    while(fin >> symbol){
        if (isdigit(symbol)){
            result.push(symbol - '0');
            continue;
        }
        int second = result.top();
        result.pop();
        int first = result.top();
        result.pop();
        if (symbol == '-')
            result.push(first - second);
        else if (symbol == '+')
            result.push(first + second);
        else if (symbol == '*')
            result.push(first * second);
    }
    fout << result.top();
    return 0;
}