/in/foo.c: In function 'main':
/in/foo.c:4:8: warning: 'main' is normally a non-static function [-Wmain]
 {  int main() {
        ^~~~
/in/foo.c: In function 'main':
/in/foo.c:10:16: warning: implicit declaration of function 'factorial' [-Wimplicit-function-declaration]
         sum += factorial(i);
                ^~~~~~~~~
/in/foo.c:12:12: warning: too many arguments for format [-Wformat-extra-args]
     printf("d\n", n, sum);
            ^~~~~
/in/foo.c: In function 'main':
/in/foo.c:14:1: error: expected declaration or statement at end of input
 }
 ^
At top level:
/in/foo.c:4:8: warning: 'main' defined but not used [-Wunused-function]
 {  int main() {
        ^~~~