Compilare: user.cpp: In function ‘int main()’: user.cpp:18:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("superstring.in","r",stdin); ^ user.cpp:19:42: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("superstring.out","w",stdout); ^ user.cpp:21:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d ",&n); ^ user.cpp:24:18: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s+1); n1=strlen(s+1); ^ user.cpp:25:19: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(ss+1); n2=strlen(ss+1); ^ /tmp/ccLteQzE.o: In function `main': user.cpp:(.text.startup+0x7f): warning: the `gets' function is dangerous and should not be used.