0_0_39709448_18240.cpp 0_0_39709448_18240.cpp(6) : error C2065: “cin”: 未声明的标识符 0_0_39709448_18240.cpp(9) : error C2065: “cin”: 未声明的标识符 0_0_39709448_18240.cpp(15) : error C2065: “cout”: 未声明的标识符