#include <iostream>
using namespace std;
int main() {
    string s = "Hello world";
    cout<<s.find("d")<<endl;
    string s1 = "Herld";
    cout<<s.compare(s1)<<endl;
    
    s.replace(3,6,"Arun");
    cout<<s<<endl;
    
    string k = "100";
    cout<<k+200<<endl;
    return 0;
}