View Compilation Error

0_0_30777991_21437.cpp: In function 'int main()':
0_0_30777991_21437.cpp:14:14: error: unable to find numeric literal operator 'operator""sum'
     else if((3sum)>=150&&(sum)<400)
              ^
0_0_30777991_21437.cpp:14:14: note: use -std=gnu++11 or -fext-numeric-literals to enable more built-in suffixes