How can I fix this problem. Pls help me (C programming)

#include <stdio.h>
#include <stdlib.h>

int main()
{
    //sum = a*b*c + (a*b-4)/2;
    double = a,b,c,sum;
    printf("a,b,c enter : ");
    scanf("%lf%lf%lf", &a, &b, &c);
    sum = a*b*c + (a*b-4)/2;
    printf("Sum : %lf", sum);
    return 0;
}

In this code, it shows error this line -> (double = a,b,c,sum;). pls help me. (I'm starter and I coudn't solve this problem). Thank you so much