Compilare: main.c: In function 'main': main.c:14:27: warning: unused variable 'aux' [-Wunused-variable] char a[250001] = {0}, aux; ^~~ main.c:13:29: warning: unused variable 'index' [-Wunused-variable] int n, i, j, N, nr = 0, index; ^~~~~ main.c:13:9: warning: unused variable 'n' [-Wunused-variable] int n, i, j, N, nr = 0, index; ^ main.c:17:5: warning: ignoring return value of 'fscanf', declared with attribute warn_unused_result [-Wunused-result] fscanf(in,"%d",&N); ^~~~~~~~~~~~~~~~~~