0_0_39256708_23312.cpp 0_0_39256708_23312.cpp(6) : error C2065: “cin”: 未声明的标识符 0_0_39256708_23312.cpp(10) : error C3861: “sqrt”: 找不到标识符 0_0_39256708_23312.cpp(12) : error C3861: “printf”: 找不到标识符