expect unqualified-id before

'<' token

This error message is typically seen when the compiler encounters a syntax error in the code. In this case, it means that there is an unexpected '<' character in the code, and the compiler doesn't know what to do with it.

The most common cause of this error is a missing semicolon at the end of a statement, which can cause the compiler to interpret the following line of code as a continuation of the previous line. Another common cause is a missing header file, which can cause the compiler to fail to recognize a particular function or data type.

To fix this error, carefully check the syntax of the code and make sure that all statements are properly terminated with semicolons. Also, make sure that all necessary header files are included in the code.