View Compilation Error

0_0_36058635_31806.cpp: In function 'int main()':
0_0_36058635_31806.cpp:16:7: error: unable to find numeric literal operator 'operator""b'
   ans=2b+a*pi;
       ^
0_0_36058635_31806.cpp:16:7: note: use -std=gnu++11 or -fext-numeric-literals to enable more built-in suffixes