C program -special characters in output

Output of this program gives a special character in the beginning.Wat is the reason?

#include<stdio.h>
#include<conio.h>
#include<string.h>
main() {
    int i, j,count=0,nl;
    char str2[100];
    char str1[100];
    char str[100];
    char init[8];
    char final[8];
    //clrscr();
    printf("enter the bit string:  ");
    gets(str);

    puts(str);
    strcat(init,"10101010");
    strcat(final,"10101010");
    strcpy(str1,(strcat(init,str)));
    strcpy(str2,(strcat(str1,final)));
    puts(str2);
    printf("%d",(strlen(str2)));
    getch();
}