Compilare: user.cpp: In function ‘int main()’: user.cpp:28:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(s[k] != ' ' && k < strlen(s)){ ^ user.cpp:37:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j = 0; j < l[i].size(); j++){ ^ user.cpp:18:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("alpin.in", "r", stdin); ^ user.cpp:19:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("alpin.out", "w", stdout); ^ user.cpp:20:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n", &n); ^ user.cpp:25:10: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s); ^ /tmp/cctfHiVh.o: In function `main': user.cpp:(.text.startup+0xd6): warning: the `gets' function is dangerous and should not be used.