Operating a long int with an int is not working

[Vorantry]

Hello,
I'm having trouble trying to operate with long int and int variables. The long int variables are stored in an array, and when I print an operation like this:

#include <stdio.h>

int main(void) {
    long int numbers[3] = {1, 2, 3};
    printf("%ld\n", ((numbers[2] * numbers[2]) - (4 * numbers[1] * numbers[3])));
    return 0;
}

I'm getting results like -6855564848099805175 or 5150792580894394377.

Type casting is not working either:

#include <stdio.h>

int main(void) {
    long int numbers[3] = {1, 2, 3};
    printf("%ld\n", (long int)((numbers[2] * numbers[2]) - (4 * numbers[1] * numbers[3])));
    return 0;
}

Why is the operation not being done successfully?
I'm using GCC 7.3.0.

Thanks in advance.

[john.c]

Array indices start at 0. An array with 3 elements is indexed with 0, 1, and 2. An index of 3 is outside the array.

[Vorantry]

Oh dear! I cannot believe I made that mistake. Definitively assigning the values 1, 2 and 3 to the array elements confused me.

Thank you very much for your help, john.c.