foo.cpp:6:41: error: expected ',' or '...' before '?' token
 bool judge(string s1,string s2,string s3?int n)  
                                         ^
foo.cpp: In function 'int main()':
foo.cpp:26:21: error: too many arguments to function 'bool judge(std::string, std::string, std::string)'
  if(judge(s1,s2,s3,n))
                     ^
foo.cpp:6:6: note: declared here
 bool judge(string s1,string s2,string s3?int n)  
      ^
foo.cpp:28:26: error: too many arguments to function 'bool judge(std::string, std::string, std::string)'
  else if(judge(s2,s1,s3,n))
                          ^
foo.cpp:6:6: note: declared here
 bool judge(string s1,string s2,string s3?int n)  
      ^
foo.cpp:30:26: error: too many arguments to function 'bool judge(std::string, std::string, std::string)'
  else if(judge(s3,s2,s1,n))
                          ^
foo.cpp:6:6: note: declared here
 bool judge(string s1,string s2,string s3?int n)  
      ^