src.cpp: In function 'int main()':
src.cpp:37:32: error: 'stdin' was not declared in this scope
freopen("BACTHANG.INP","r",stdin);
^
src.cpp:37:37: error: 'freopen' was not declared in this scope
freopen("BACTHANG.INP","r",stdin);
^
src.cpp:38:32: error: 'stdout' was not declared in this scope
freopen("BACTHANG.OUT","w",stdout);
^