View Compilation Error

0_0_30432074_11905.cpp: In function 'long long int lucas(long long int, long long int, long long int)':
0_0_30432074_11905.cpp:25:6: error: 'a' was not declared in this scope
   if(a<b) return 0;
      ^
0_0_30432074_11905.cpp:25:8: error: 'b' was not declared in this scope
   if(a<b) return 0;
        ^