/in/foo.c: In function 'main':
/in/foo.c:8:23: warning: statement with no effect [-Wunused-value]
    for (i = 0; i++; i <= n)
                     ~~^~~~
/in/foo.c:14:5: warning: 'Sn' is used uninitialized in this function [-Wuninitialized]
     printf("%d", Sn);
     ^~~~~~~~~~~~~~~~