#include <stdio.h>

float dotprod3(float x[3], float y[3]);

int main() {
    float a[3], b[3];
    float d;

    printf("Ax, Ay, Az: ");
    scanf("%f, %f, %f",
	  &a[0], &a[1], &a[2]);

    printf("Bx, By, Bz: ");
    scanf("%f, %f, %f",
	  &b[0], &b[1], &b[2]);

    d = dotprod3(a, b);
    printf("Dot product: %f\n", d);
    return 0;
}

float dotprod3(float x[3], float y[3])
{
    return x[0]*y[0] + x[1]*y[1]
	+ x[2]*y[2];
}