Compilare: user.cpp: In function ‘int main()’: user.cpp:12:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0;i<strlen(s);i++) ^ user.cpp:17:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0;i<strlen(s);i++) ^ user.cpp:8:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("puzzle.in","r",stdin); ^ user.cpp:9:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("puzzle.out","w",stdout); ^ user.cpp:10:12: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s); ^ user.cpp:11:13: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s1); ^ /tmp/cc1dONNk.o: In function `main': user.cpp:(.text.startup+0x58): warning: the `gets' function is dangerous and should not be used.