poly* multiplication(poly *a, poly *b)
{
    int i, j, k = 0;
    poly *c = (poly*)malloc(sizeof(poly));
    c->pow = a->pow + b->pow;
    c->data = (int*)malloc(sizeof(int)*c->pow+1);
    int **coefficient;
    coefficient = (int**)malloc(sizeof(int*)*a->pow+1);
    for (i = 0; i < a->pow+1; i++)
    {
        coefficient[i] = (int*)malloc(sizeof(int)*b->pow+1);
    }
    for (i = 0; i < a->pow+1; i++)
    {
        for (j = 0; j < b->pow+1; j++)
        {
            coefficient[i][j] = 0;
            coefficient[i][j] = a->data[i] * b->data[j];
        }
    }
    for (k = 0; k < a->pow+1; k++)
    {
        for (i = k, j = 0; i < k; i--, j++)
        {
            c->data[k] += coefficient[i][j];
        }
    }
    for (k = a->pow+1; k < a->pow+ b->pow +1; k++)
    {
        for (i = a->pow, j = k-a->pow; j < a->pow+1; i--, j++)
        {
            c->data[k] += coefficient[i][j];
        }