foo.cc: In function 'int jc(int, int)':
foo.cc:27:7: warning: statement has no effect [-Wunused-value]
  for(n;n>1;n--)
       ^
foo.cc: In function 'int main()':
foo.cc:21:13: warning: 'i' may be used uninitialized in this function [-Wmaybe-uninitialized]
     cout<<i-1<<endl;
             ^