/in/foo.c: In function 'main':
/in/foo.c:9:10: warning: statement with no effect [-Wunused-value]
      ret + ret * i;
      ~~~~^~~~~~~~~
/in/foo.c:7:4: warning: 'n' is used uninitialized in this function [-Wuninitialized]
    for (i = 1; i <= n; i++)
    ^~~