#include <stdio.h>
int main(void) {
int a, b, c, d, e, min, max, ;
scanf("%d%d%d%d%d", &a, &b, &c, &d, &e);
min = a;
if (b < min) min = b;
if (c < min) min = c;
if (d < min) min = d;
if (e < min) min = e;
max = a;
if (max < b) max = b;
if (max < c) max = c;
if (max < d) max = d;
if (max < e) max = e;
printf("%d\n", max * min);
return 0;
}