#include <cstdio> #include <iostream> #include <fstream> #include <vector> #include <list> #include <map> #include <set> #include <queue> #include <stack> #include <bitset> #include <algorithm> #include <sstream> #include <iomanip> #include <cmath> #include <cstdlib> #include <cctype> #include <cstring> #include <string> #include <ctime> #include <cassert> #include <utility> using namespace std; int A[5]; int main() { // freopen("date.in", "r", stdin); for(int i = 0; i < 4; i++) scanf("%d", &A[i]); vector<int> perm(4); for(int i = 0; i < 4; i++) perm[i] = i; int ans = 0; do { int a = A[perm[0]]; int b = A[perm[1]]; int c = A[perm[2]]; int d = A[perm[3]]; ans = max(ans, a * b + c * d); } while(next_permutation(perm.begin(), perm.end())); printf("%d\n", ans); return 0; }