Main.c: In function 'main':
Main.c:10:19: warning: implicit declaration of function 'jiecheng' [-Wimplicit-function-declaration]
   10 |     printf("%lld",jiecheng(num));
      |                   ^~~~~~~~
Main.c:10:16: warning: format '%lld' expects argument of type 'long long int', but argument 2 has type 'int' [-Wformat=]
   10 |     printf("%lld",jiecheng(num));
      |             ~~~^  ~~~~~~~~~~~~~
      |                |  |
      |                |  int
      |                long long int
      |             %d
Main.c: At top level:
Main.c:14:15: error: conflicting types for 'jiecheng'; have 'long long int(int)'
   14 | long long int jiecheng(int num){
      |               ^~~~~~~~
Main.c:10:19: note: previous implicit declaration of 'jiecheng' with type 'int()'
   10 |     printf("%lld",jiecheng(num));
      |                   ^~~~~~~~