stack

#include <iostream>
#include <stack>
#include <string>
#include <vector>
#include <algorithm>

using namespace std;

vector <string> sig = {"*", "/", "+", "-"};

bool sgn(string x){
    bool r = 0;
    for (auto y: sig){
        if (y == x){
            r = 1;
        }
    }
    return r;
}

int opr(string x, int a, int b){
    int res;
    if (x == "*") res = a * b;
    else if (x == "/") res = a / b;
    else if (x == "+") res = a + b;
    else if (x == "-") res = a - b;
    return res;
}

int main()
{
    vector <string> al;
    stack <int> go;
    string s;
    getline(cin, s);
    /*for (char l: s){
        cout<<l<<'\n';
    }*/
    int id = 0;
    string x = "";
    for (int i=0;i<s.size();++i){
            char l = s[i];
            if (l == ' ') {
                    //cout<<i<<'\n';
                    al.push_back(x);
                    x = "";

            }
            else{
                x += l;
            }
    }
    al.push_back(x);
    //for (auto x: al) cout<<x<<'\n';
    int dg;
    int a,b;
    int ans = 0;
    for (auto x: al){
        if (sgn(x)){
            //cout<<x<<'\n';
            a = go.top();
            go.pop();
            b = go.top();
            go.pop();
            ans = opr(x, a, b);
            go.push(ans);
        }
        else {
            dg = stoi(x);
            go.push(dg);
        }
    }
    cout<<"ans= "<<ans<<'\n';
}