double* my_solver(int N, double* A, double *B) {
    printf("NEOPT SOLVER\n");
    register int i, j, k = 0;


    register double* Apatrat = (double*)calloc(N *N, sizeof(double));
    //if(Apatrat == NULL) return NULL;

    register double* C = (double*)calloc(N *N, sizeof(double));
    //  if(C == NULL) return NULL;

    //int dim = N * N;

    double* ap = Apatrat;
    double* a = A;
    double* au = A;
    int dim = N * N;
    register int t = 0;

    for (t = 0, i = 0; i < dim; i += N, ++t) {
        for (j = t; j < N; j++) {
            a = A + i + t;
            au = A + i + j;
            for (k = t; k <= j; k++) {
                *ap += (*a) * (*au);
                ++a;
                au += N;
            }
            ++ap;
        }
        ap += t + 1;
    }

    // calculez B x A
    double* c = C;
    double* b = B;
    for (i = 0; i < dim; i += N) {
        for (j = 0; j < N; j++) {
            b = B + i + j;
            a = A + j * N + j;
            for (k = j; k < N; k++) {
                *c += (*b) * (*a);
                ++b;
                ++a;
            }
            ++c;
        }
    }

    c = C;
    for (t = 0, i = 0; i < N; i++, t += N) {
        for (j = 0; j < N; j++) {
            ap = Apatrat + t + i;
            b = B + t + j;
            for (k = i; k < N; k++) {
                *c += (*ap) * (*b);
                ++ap;
                b += N;
            }
            ++c;
        }
    }

    return C;
}