Compilare: user.cpp: In function ‘int main()’: user.cpp:16:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("k1.in","r",stdin); ^ user.cpp:17:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("k1.out","w",stdout); ^ user.cpp:19:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lld\n", &n); ^ user.cpp:23:23: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(buff + 1); long long lg = strlen(buff + 1); ^ /tmp/ccxFy5Bu.o: In function `main': user.cpp:(.text.startup+0x98): warning: the `gets' function is dangerous and should not be used.