Program in C to concatenate two strings

#include
#include
#include
void main()
{
            char str1[20],str2[20],str3[50],ch;
            int len1,len2,i,j;
            clrscr();
            printf("\n Enter the String 1:-");
            scanf("%s",&str1);
            printf("\n Enter the String 2:-");
            scanf("%s",&str2);
            for(len1=0;str1[len1]!='\0';len1++);
            for(len2=0;str2[len2]!='\0';len2++);
            for(i=0;i<(len1+len2);i++)      
            {
            if(i             {
            str3[i]=str1[i];
            j=0;
            }
            else
            {
            str3[i]=str2[j];
            j++;
            }
            }
            str3[i]='\0';
            printf("\n%s + %s = %s",str1,str2,str3);
getch();
}

Output