0_0_13626122_17629.cpp 0_0_13626122_17629.cpp(7) : error C2065: “o”: 未声明的标识符 0_0_13626122_17629.cpp(10) : error C2065: “sum”: 未声明的标识符 0_0_13626122_17629.cpp(12) : error C2065: “sum”: 未声明的标识符 0_0_13626122_17629.cpp(15) : error C2065: “sum”: 未声明的标识符