Compilare: user.cpp: In function ‘void solve()’: user.cpp:26:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(d.size() == k) ^ user.cpp: In function ‘void read()’: user.cpp:13:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("par.in", "r", stdin); ^ user.cpp:14:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("par.out", "w", stdout); ^ user.cpp:15:22: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n", &n); ^ user.cpp:16:16: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s + 1); ^ /tmp/cc4VXTQ7.o: In function `read()': user.cpp:(.text+0x61): warning: the `gets' function is dangerous and should not be used.