View Compilation Error

0_0_25856932_20199.cpp: In function 'int main()':
0_0_25856932_20199.cpp:188:13: error: 'IO' has not been declared
             IO::read(op), IO::read(x), IO::read(y);
             ^
0_0_25856932_20199.cpp:188:27: error: 'IO' has not been declared
             IO::read(op), IO::read(x), IO::read(y);
                           ^
0_0_25856932_20199.cpp:188:40: error: 'IO' has not been declared
             IO::read(op), IO::read(x), IO::read(y);
                                        ^