View Compilation Error

0_0_38435429_7659.cpp:4:6: error: 'x' was not declared in this scope
 ll f(x)
      ^
0_0_38435429_7659.cpp:5:1: error: expected ',' or ';' before '{' token
 {
 ^
0_0_38435429_7659.cpp: In function 'int main()':
0_0_38435429_7659.cpp:19:28: error: 'f' cannot be used as a function
         printf("%lld\n",f(n));
                            ^