foo.cc: In function 'bool Prime(int)':
foo.cc:8:5: error: expected unqualified-id before 'for'
     for (i=2;i<n/2;i++){
     ^~~
foo.cc:8:15: warning: statement has no effect [-Wunused-value]
     for (i=2;i<n/2;i++){
              ~^~~~
foo.cc:8:23: error: expected ';' before ')' token
     for (i=2;i<n/2;i++){
                       ^
foo.cc: In function 'int main()':
foo.cc:19:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (i=0; i<word.size(); i++)
               ~^~~~~~~~~~~~

自豪的采用jd5进行评测(github.com/masnn/jd5)