Compilare: user.cpp: In function ‘int main()’: user.cpp:11:5: warning: ‘char* gets(char*)’ is deprecated [-Wdeprecated-declarations] gets(a); ^ In file included from /usr/include/c++/5/cstdio:42:0, from user.cpp:1: /usr/include/stdio.h:638:14: note: declared here extern char *gets (char *__s) __wur __attribute_deprecated__; ^ user.cpp:11:5: warning: ‘char* gets(char*)’ is deprecated [-Wdeprecated-declarations] gets(a); ^ In file included from /usr/include/c++/5/cstdio:42:0, from user.cpp:1: /usr/include/stdio.h:638:14: note: declared here extern char *gets (char *__s) __wur __attribute_deprecated__; ^ user.cpp:11:11: warning: ‘char* gets(char*)’ is deprecated [-Wdeprecated-declarations] gets(a); ^ In file included from /usr/include/c++/5/cstdio:42:0, from user.cpp:1: /usr/include/stdio.h:638:14: note: declared here extern char *gets (char *__s) __wur __attribute_deprecated__; ^ user.cpp:45:37: warning: integer overflow in expression [-Woverflow] c[i][j]=unsigned((1<<31)-1); ^ user.cpp:8:33: 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:9:35: 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:10:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%u\n",&k); ^ user.cpp:11:12: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(a); ^ /tmp/ccBvUqPG.o: In function `main': user.cpp:(.text.startup+0x51): warning: the `gets' function is dangerous and should not be used.