View Compilation Error

0_0_27772544_26171.cpp:4:20: error: 'n' was not declared in this scope
 long long int rule(n)
                    ^
0_0_27772544_26171.cpp:5:1: error: expected ',' or ';' before '{' token
 {
 ^
0_0_27772544_26171.cpp: In function 'int main(int, const char**)':
0_0_27772544_26171.cpp:27:46: error: 'rule' cannot be used as a function
   printf("%lld\n", C(total, wrong)*rule(wrong));
                                              ^