double sum (double a, double b){
    return a + b;
}

double ruz(double a, double b){
    return a-b;
}

double mng (double a, double b){
    return a*b;
}

double del (double a, double b){
    return a/b;
}

int main() {
    stdout.printf ("chislo\n");
        double a=double.parse (stdin.read_line ());
    stdout.printf ("drugoe chislo\n");
        double b= double.parse (stdin.read_line ());
    stdout.printf ("deystvie\n");
        string c=stdin.read_line ();
        if ( c == "sum") {
            stdout.printf (@"$(sum( a, b))\n");
        }
        else if  ( c== "ruz"){
            stdout.printf (@"$(ruz(a,b))\n");
        }
        else if (c== "mng"){
            stdout.printf (@"$(mng(a,b))\n");
        }
        else if (c== "del"){
            stdout.printf (@"$(del(a,b))\n");
        }

    return 0;
}