foo.cpp: In function 'int main()':
foo.cpp:17:34: error: 'stdin' was not declared in this scope
         freopen("matches.in","r",stdin);
                                  ^
foo.cpp:17:39: error: 'freopen' was not declared in this scope
         freopen("matches.in","r",stdin);
                                       ^
foo.cpp:18:35: error: 'stdout' was not declared in this scope
         freopen("matches.out","w",stdout);
                                   ^