Compilare: user.cpp: In function ‘int main()’: user.cpp:27:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=1;i<=n;i++) ^ user.cpp:28:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=1;j<=n;j++) ^ user.cpp:35:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=k+1;i<=n;i++) ^ user.cpp:45:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=2;i<=n;i++) ^ user.cpp:18:29: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("blis.in","r",stdin); ^ user.cpp:19:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("blis.out","w",stdout); ^ user.cpp:20:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%c",&k,&c); ^ user.cpp:21:8: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s); ^ /tmp/ccQbOxLE.o: In function `main': user.cpp:(.text.startup+0x77): warning: the `gets' function is dangerous and should not be used.