If I need "BEYONDKnowing" as output what should be the input to this particular problem below?

#include <stdio.h>
int main()
{
   char str1[50], str2[50], i, j;
   printf("\nEnter first string: ");
   scanf("%s",str1);
   printf("\nEnter second string: ");
   scanf("%s",str2);
for(i=0; str1[i]!='\0'; ++i); 0
for(j=0; str2[j]!='\0'; ++j, ++i)
   {
      str1[i]=str2[j];
   }
   str1[i]='\0';
   printf("\nOutput: %s",str1);
   
   return 0;
}