View Compilation Error

0_0_29399314_16350.cpp: In member function 'int Palindromic_Tree::get_fail(int)':
0_0_29399314_16350.cpp:41:29: error: expected ')' before '!' token
   while ( S[n - len[x] - 1] ! = S[n] ) x = fail[x] ;
                             ^
0_0_29399314_16350.cpp:41:31: error: expected primary-expression before '=' token
   while ( S[n - len[x] - 1] ! = S[n] ) x = fail[x] ;
                               ^