storage - c++: How to store the rest of the string in a variable? -

hey guys have question storing output variable. let's have 3 variables defined follows:

float num,  string units,  string rest; 

and user enters in console:

 12.2  mg   vitamin 

i know if want store in variables, have following:

cin >> num >> units >> rest; 

but let's user enters vitamin instead of vitamin.

and want store rest of string after mg 'rest' variable. how do that?

i did following:

cin >> num >> units; getline(cin,rest); //stores rest of string rest 

but stores space character after mg namely if output rest, output " vitamin a". don't want space in beginning. how accomplish this?

i know it's long hope made clear. or suggestions helpful. thanks,

you can skip whitespace using std::ws

cin >> num >> units; ws(cin); getline(cin, rest); 

you can see live working example here: ignore leading whitespace