#include <iostream>
#include <string>
using namespace std;
int main () {
string str1 = "Hello";
string str2 = "World";
string str3;
int len ;
// copy str1 into str3
str3 = str1;
cout << "str3 : " << str3 << endl;
// concatenates str1 and str2
str3 = str1 + str2;
cout << "str1 + str2 : " << str3 << endl;
// total lenghth of str3 after concatenation
len = str3.size();
cout << "str3.size() : " << len << endl;
return 0;
}
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