View Compilation Error

0_0_37283482_7358.cpp: In function 'void sum(long long int)':
0_0_37283482_7358.cpp:24:11: error: 'find' was not declared in this scope
   find(2*k);
           ^
0_0_37283482_7358.cpp: In function 'int main()':
0_0_37283482_7358.cpp:36:9: error: 'find' was not declared in this scope
   find(1);
         ^