for(int k = 0; k<=Na-Nb; k++){
        thirdSum[k] = new Complex(0,0);
      for(int j = 0; j<Nb; j++){
        thirdSum[k] = thirdSum[k].plus(b[j].times(a[(Na-k-1)+j]));
      }
    }
    for(int i= Na-Nb+1; i < N; i++){
      thirdSum[i] = new Complex(0,0);
    }
    thirdSum = inverse_FFT(thirdSum,N);
    for(int k = 0; k<=Na-Nb; k++){
     System.out.print( k + ", Second Sum = " + secondSum[k] + ", ");
     System.out.println("Third Sum = " + thirdSum[k]);
    }

    }