void mat_mult(int **mat1, int **mat2, size_t *matrices_size, int **out)
{
    size_t  n = matrices_size[0];
    size_t  m = matrices_size[1];
    size_t  p = matrices_size[2];
    int sum = 0;
    for (size_t i = 0; i < n; i++)
    {
        for (size_t j = 0; j < p; j++)
        {
            sum = 0;
            for (size_t k = 0; k < m; k++)
            {
                sum += mat1[i][k] * mat2[k][j];
            }
            out[i][j] = sum;
        }
    }
}