#include<bits/stdc++.h>
using namespace std;

vector<string> comb;
int n;

void rec (int i,string s) {
	if (i == n) {
		comb.push_back(s);
		return;
	}
	rec(i + 1,s + '0');
	rec(i + 1,s + '1');
}

int main () {
	 ios::sync_with_stdio(false);
	 cin.tie(nullptr);
	 cout.tie(nullptr);
	 string N;
	 cin >> N;
	 n = (int) N.size();
	 rec(0,"");
	 int64_t res = 0;
	 for (string s : comb) {
		 vector<int> x,y;
		 for (int i = 0; i < n; ++i) {
			 if (s[i] == '1') {
				 x.push_back(N[i] - '0');
			 } else {
				 y.push_back(N[i] - '0');
			 }
		 }
		 sort(x.rbegin(),x.rend());
		 sort(y.rbegin(),y.rend());
		 int64_t x1 = 0,y1 = 0;
		 for (int i = 0; i < (int) x.size(); ++i) {
			 x1 = x1 * 10 + x[i];
		 }
		 for (int i = 0; i < (int) y.size(); ++i) {
			 y1 = y1 * 10 + y[i];
		 }
		 res = max(res,x1 * y1);
	 }
	 cout << res << '\n';
}