#include <iostream>
#include <map>
#include <string>
#include <sstream>
#include <vector>
#include <algorithm>
#include <functional>
#include <stdexcept>
using namespace std;
#include <ginac/ginac.h>
using namespace GiNaC;

// Shamelessly ripped from GiNaC FAQ :)

const symbol symbol_factory(const int & i_ ) {
    static map<int, symbol> directory;
    map<int, symbol>::iterator i = directory.find(i_);
    if (i!=directory.end())
        return i->second;
		ostringstream so ;
		so << "s" << i_;
		string s = so.str();
    return directory.insert(map<int, symbol>::value_type(i_, symbol(s))).first->second;
}

// I'm not sure if you really need indexed things...

ex Z (const int & n) {
	if ( n == 0 )
		return ex(1);

	ex result(0);
	for (int j = 1; j <= n; j++ )
			result += (symbol_factory(j)*Z(n-j)).expand();
		return result;
}

int main(int argc, char** argv) {
	int arg = 3;
	if(argc >= 2)
		arg = atoi(argv[1]);
	cout << "Z(" << arg << ") = " << Z(arg) << endl;
	return 0;
}