How do i use str::at

Question

How do I use str.at or some other way to read string position. Example string "hello"
I could read 4 position in this it would be "l"

Answer 1

Eg :

string s = "Hello";
cout<<s.at(4)<<endl;

Answer 2

index of o will be 4 & posn will be 5
//btw in hello there are 2l's