homework problem for C++ a beginer c++ .

Write the function first Not ln (). The function has two parameters; const char * str and const char * chars. The first is the C - style string to search, and the second is a C - style string containing characters to exclude. The function returns the index (as a size_t) of the first occurrence of any character from str that does not appear inside chars. If all of the characters inside str appear inside chars, return the value size_t (-1). You cannot use any library functions for this problem. You may use array or pointer notation