View Compilation Error

0_0_18407166_16883.cpp: In function 'int main()':
0_0_18407166_16883.cpp:18:16: error: unable to find numeric literal operator 'operator""k'
         ll ans=0.k;
                ^
0_0_18407166_16883.cpp:18:16: note: use -std=gnu++11 or -fext-numeric-literals to enable more built-in suffixes
0_0_18407166_16883.cpp:20:17: error: 'k' was not declared in this scope
         for(i=0,k=0;i<=len;i++)
                 ^