/in/foo.cc: In function 'int main()':
/in/foo.cc:9:12: warning: right operand of comma operator has no effect [-Wunused-value]
    cin>>a,b;
            ^
/in/foo.cc:11:13: warning: right operand of comma operator has no effect [-Wunused-value]
    cout<<A,B;
             ^
/in/foo.cc:8:13: warning: 'A' is used uninitialized in this function [-Wuninitialized]
    char a,b,A,B;
             ^