View Compilation Error

0_0_38550796_1767.cpp: In function 'int main()':
0_0_38550796_1767.cpp:10:26: error: unable to find numeric literal operator 'operator""B'
   a=sqrt((x1-x2)*(x1-x2)%2B(y1-y2)*(y1-y2));
                          ^
0_0_38550796_1767.cpp:10:26: note: use -std=gnu++11 or -fext-numeric-literals to enable more built-in suffixes