View Compilation Error

0_0_29503072_14668.cpp: In function 'int main()':
0_0_29503072_14668.cpp:18:16: error: unable to find numeric literal operator 'operator""maxn'
  for(int i=4;i<2maxn;i++)
                ^
0_0_29503072_14668.cpp:18:16: note: use -std=gnu++11 or -fext-numeric-literals to enable more built-in suffixes