/in/foo.cc: In function 'int main()':
/in/foo.cc:9:21: error: 'GetBig' was not declared in this scope
   int big  =GetBig(n); // 最大数
                     ^
/in/foo.cc:10:23: error: 'GetSmall' was not declared in this scope
   int small=GetSmall(n);  // 最小数
                       ^
/in/foo.cc: In function 'int GetBig(int)':
/in/foo.cc:25:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^