View Compilation Error

0_0_35700513_8420.cpp: In function 'll calc(ll)':
0_0_35700513_8420.cpp:7:30: error: 'a' was not declared in this scope
         ll add = min(n-i,min(a - i % a,b - i % b));
                              ^
0_0_35700513_8420.cpp:7:40: error: 'b' was not declared in this scope
         ll add = min(n-i,min(a - i % a,b - i % b));
                                        ^