Compilare: user.cpp: In function ‘void read()’: user.cpp:66:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("sub.in", "r", stdin); ^ user.cpp:67:22: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n", &n); ^ user.cpp:72:20: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(w + 1); ^ user.cpp: In function ‘void solve()’: user.cpp:81:22: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n", &m); ^ user.cpp:84:20: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(w + 1); ^ user.cpp: In function ‘void write()’: user.cpp:97:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("sub.out", "w", stdout); ^ /tmp/ccY3u4vp.o: In function `read()': user.cpp:(.text+0x1d3): warning: the `gets' function is dangerous and should not be used.