/in/foo.cc: In constructor 'Mat::Mat()':
/in/foo.cc:12:45: error: 'memset' was not declared in this scope
         memset(this->dat,0,sizeof(this->dat));
                                             ^
/in/foo.cc: In function 'void init()':
/in/foo.cc:41:28: error: 'memset' was not declared in this scope
     memset(at,-1,sizeof(at));
                            ^
/in/foo.cc: In function 'void solve()':
/in/foo.cc:55:9: warning: unused variable 'u' [-Wunused-variable]
     int u,v;
         ^