View Compilation Error

0_0_38550709_7895.cpp: In function 'int main()':
0_0_38550709_7895.cpp:8:28: error: unable to find numeric literal operator 'operator""B'
     m=sqrt((x1-x2)*(x1-x2)%2B(y1-y2)*(y1-y2));
                            ^
0_0_38550709_7895.cpp:8:28: note: use -std=gnu++11 or -fext-numeric-literals to enable more built-in suffixes
0_0_38550709_7895.cpp:8:45: error: 'sqrt' was not declared in this scope
     m=sqrt((x1-x2)*(x1-x2)%2B(y1-y2)*(y1-y2));
                                             ^