What will be the output of following code?

#include iostream  
    #include cstring  
using namespace std;  
int main ()  
    {  
char str1[10] = "Hello";  
char str2[10] = "World";  
char str3[10];  
intlen ;  
strcpy( str3, str1);  
strcat( str1, str2);  
len = strlen(str1);  
coutlenendl;  
return 0;  
    }