Compilare: main.c: In function 'main': main.c:15:12: warning: passing argument 1 of 'fscanf' from incompatible pointer type [-Wincompatible-pointer-types] fscanf("%d", &n); ^~~~ In file included from /usr/include/features.h:367:0, from /usr/include/stdio.h:27, from main.c:5: /usr/include/stdio.h:443:12: note: expected 'FILE * restrict {aka struct _IO_FILE * restrict}' but argument is of type 'char *' extern int __REDIRECT (fscanf, (FILE *__restrict __stream, ^ main.c:15:18: warning: passing argument 2 of 'fscanf' from incompatible pointer type [-Wincompatible-pointer-types] fscanf("%d", &n); ^ In file included from /usr/include/features.h:367:0, from /usr/include/stdio.h:27, from main.c:5: /usr/include/stdio.h:443:12: note: expected 'const char * restrict' but argument is of type 'int *' extern int __REDIRECT (fscanf, (FILE *__restrict __stream, ^ main.c:15:18: warning: format not a string literal and no format arguments [-Wformat-security] fscanf("%d", &n); ^~ main.c:23:13: warning: passing argument 1 of 'fprintf' from incompatible pointer type [-Wincompatible-pointer-types] fprintf("%d", nr); ^~~~ In file included from /usr/include/stdio.h:936:0, from main.c:5: /usr/include/x86_64-linux-gnu/bits/stdio2.h:95:1: note: expected 'FILE * restrict {aka struct _IO_FILE * restrict}' but argument is of type 'char *' fprintf (FILE *__restrict __stream, const char *__restrict __fmt, ...) ^~~~~~~ main.c:23:19: warning: passing argument 2 of 'fprintf' makes pointer from integer without a cast [-Wint-conversion] fprintf("%d", nr); ^~ In file included from /usr/include/stdio.h:936:0, from main.c:5: /usr/include/x86_64-linux-gnu/bits/stdio2.h:95:1: note: expected 'const char * restrict' but argument is of type 'int' fprintf (FILE *__restrict __stream, const char *__restrict __fmt, ...) ^~~~~~~ main.c:23:5: warning: format not a string literal and no format arguments [-Wformat-security] fprintf("%d", nr); ^~~~~~~ main.c:12:16: warning: variable 'out' set but not used [-Wunused-but-set-variable] FILE *in, *out; ^~~ main.c:12:11: warning: variable 'in' set but not used [-Wunused-but-set-variable] FILE *in, *out; ^~ main.c:15:5: warning: ignoring return value of 'fscanf', declared with attribute warn_unused_result [-Wunused-result] fscanf("%d", &n); ^~~~~~~~~~~~~~~~