#include <stdio.h>

int main() {

	unsigned int numar[4];
	unsigned int aux, i, j;

	for(i = 0; i < 4; i++) {
		scanf("%d", &numar[i]);
	}

	for(i = 0; i < 3; i++){
		for(j = i + 1; j < 4; j++) {
			if(numar[i] > numar[j]) {
				aux = numar[i];
				numar[i] = numar[j];
				numar[j] = aux;
			}
		}
	}

	printf("%d \n", numar[0] * numar[1] + numar[2] * numar[3]);


	return 0;
}