/in/foo.c: In function 'main':
/in/foo.c:5:9: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'scanf'
    5 |         scanf("%d",&n);
      |         ^~~~~
/in/foo.c:5:21: error: 'n' undeclared (first use in this function)
    5 |         scanf("%d",&n);
      |                     ^
/in/foo.c:5:21: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:8:25: error: expected expression before '...' token
    8 |         sum=1+1*2+1*2*3+...+1*2...i；
      |                         ^~~
/in/foo.c:8:31: error: too many decimal points in number
    8 |         sum=1+1*2+1*2*3+...+1*2...i；
      |                               ^~~~~~~
/in/foo.c:6:13: warning: variable 'sum' set but not used [-Wunused-but-set-variable]
    6 |         int sum=0;
      |             ^~~
/in/foo.c: At top level:
/in/foo.c:10:8: error: expected declaration specifiers or '...' before string constant
   10 | printf("%d\n",sum);
      |        ^~~~~~
/in/foo.c:10:15: error: unknown type name 'sum'
   10 | printf("%d\n",sum);
      |               ^~~
/in/foo.c:11:1: error: expected identifier or '(' before 'return'
   11 | return 0;
      | ^~~~~~
/in/foo.c:12:1: error: expected identifier or '(' before '}' token
   12 | }
      | ^