#include <stdio.h>
int main() {
    int qx, px,qy, py, qz, pz;
    scanf("%d %d %d %d %d %d", &qx, &px, &qy, &py, &qz, &pz);
    if (qx < 0 || qy < 0 || qz < 0 || px  0 || py < 0 || pz < 0)
        printf("Invalid input");
    else
        printf("%d", qx*px + qy*py + qz*pz);
    return 0;
}