Compilare: main.c: In function 'main': main.c:15:8: warning: implicit declaration of function 'memset' [-Wimplicit-function-declaration] memset(a, 0xff, 250001); ^~~~~~ main.c:15:8: warning: incompatible implicit declaration of built-in function 'memset' main.c:15:8: note: include '<string.h>' or provide a declaration of 'memset' main.c:13:8: warning: ignoring return value of 'fscanf', declared with attribute warn_unused_result [-Wunused-result] fscanf(in,"%d",&N); ^~~~~~~~~~~~~~~~~~