Help with the code .Does not work properly

Question

Write a program that compares two lines and displays a message about which characters match.
#include "stdafx.h"
#include <iostream>
#include <conio.h>
#include <string.h>
#define lenght 256
using namespace std;
int main()
{

char str1[lenght], str2[lenght], strnew[lenght];
cout « "Первая строка: "; cin » str1;
cout « "Вторая строка: "; cin » str2;
int a = strlen(str1);
int b = strlen(str2);
int k = 0, i = 0;
while (i <= a)
{
for (int j = 0; j <= b; j++)
if (str1[i] == str2[j])
{
strnew[k] = str1[i];
k++;
}
i++;
}
cout « "\n " « strnew « '\n';
}