Correlation using FFT | MATLAB

Code:

clc
clear all
close all
x1_n=input('Enter the first sequence');
x2_n=input('Enter the second sequence');
x2_n=fliplr(x2_n);
N=length(x1_n);
M=length(x2_n);
S=N+M-1;
X1_K=fft(x1_n,S);
X2_K=fft(x2_n,S);
X3_K=X1_K.*X2_K;
x3_n=ifft(X3_K);