/in/foo.c: In function 'main':
/in/foo.c:7:15: error: expected expression before 'int'
  if(n>100000) int a[10000000];
               ^~~
/in/foo.c:8:8: error: expected expression before 'int'
  else  int a[100000];
        ^~~
/in/foo.c:10:14: error: 'a' undeclared (first use in this function)
  scanf("%d",&a[i]);
              ^
/in/foo.c:10:14: note: each undeclared identifier is reported only once for each function it appears in