A {1,2,3,4}
B {2,1,4,9}
c {5,8,7,6}

while(getline(cin,input)){
stringstream ss(input);
string letter;

while(!ss.eof()){
ss >> letter;
if (letter == "A")
{
    Do this
}
if (letter == "B")
{
    Do this
}
if (letter== "C")
{
    Do this
}
}
}