Compilare: user.cpp: In function ‘int main()’: user.cpp:18:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("rj.in","r",stdin); ^ user.cpp:19:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("rj.out","w",stdout); ^ user.cpp:21:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d\n",&n,&m); ^ user.cpp:25:21: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(v[i]+1); ^ user.cpp:47:19: warning: ‘y2’ may be used uninitialized in this function [-Wmaybe-uninitialized] q.push({x2,y2}); ^ user.cpp:47:19: warning: ‘x2’ may be used uninitialized in this function [-Wmaybe-uninitialized] user.cpp:33:19: warning: ‘y1’ may be used uninitialized in this function [-Wmaybe-uninitialized] q.push({x1,y1}); ^ user.cpp:33:19: warning: ‘x1’ may be used uninitialized in this function [-Wmaybe-uninitialized] In file included from /usr/include/stdio.h:934:0, from /usr/include/c++/4.8/cstdio:42, from user.cpp:1: In function ‘char* gets(char*)’, inlined from ‘int main()’ at user.cpp:25:21: /usr/include/i386-linux-gnu/bits/stdio2.h:230:28: warning: call to ‘__gets_warn’ declared with attribute warning: please use fgets or getline instead, gets can't specify buffer size [enabled by default] return __gets_warn (__str); ^ /tmp/ccSyoEyY.o: In function `main': user.cpp:(.text.startup+0xfa): warning: the `gets' function is dangerous and should not be used.