/in/foo.cc: In function 'int isRunNian(int)':
/in/foo.cc:18:4: error: 'a' was not declared in this scope
    a = 0;
    ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:26:9: error: 'a' was not declared in this scope
     if (a == 1){
         ^
/in/foo.cc: In function 'int isRunNian(int)':
/in/foo.cc:21:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^