/in/foo.cc: In function 'int main()':
/in/foo.cc:14:21: warning: format '%[^
' expects argument of type 'char*', but argument 2 has type 'char (*)[100]' [-Wformat=]
    scanf("%[^\n]",&a);
                     ^
/in/foo.cc:16:21: warning: format '%[^
' expects argument of type 'char*', but argument 2 has type 'char (*)[100]' [-Wformat=]
    scanf("%[^\n]",&b);
                     ^
/in/foo.cc:14:22: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%[^\n]",&a);
                      ^
/in/foo.cc:16:22: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%[^\n]",&b);
                      ^