运行 ID: 47194

Main.cc: In function ‘int main()’:
Main.cc:6:2: error: ‘in’ was not declared in this scope
  in>>a;
  ^~
Main.cc:6:2: note: suggested alternative: ‘yn’
  in>>a;
  ^~
  yn
Main.cc:8:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i