View Compilation Error

0_0_26078976_12126.cpp: In function 'int main()':
0_0_26078976_12126.cpp:17:24: error: unable to find numeric literal operator 'operator""n'
         for(int i=1;i<=3n;i++){
                        ^
0_0_26078976_12126.cpp:17:24: note: use -std=gnu++11 or -fext-numeric-literals to enable more built-in suffixes