c++11: unable to find numeric literal operator ‘operator""

I'm trying to create an array with inside: 1_0R 1_5R 2_0R

char height[] = { 1_0R , 1_5R , 2_0R };

because i'm working with i/o files, and the string mentioned are inside the filenames. I use +to_string( height[1] )+

When I compile i get the 3 errors

 **error: unable to find numeric literal operator ‘operator""_0R’**
 **error: unable to find numeric literal operator ‘operator""_5R’**
 **error: unable to find numeric literal operator ‘operator""_0R’**

what can i do?