Compilare: user.c: In function ‘main’: user.c:34:9: warning: implicit declaration of function ‘strlen’ [-Wimplicit-function-declaration] last_2_digits = n[strlen(n) - 1] - '0'; ^ user.c:34:27: warning: incompatible implicit declaration of built-in function ‘strlen’ [enabled by default] last_2_digits = n[strlen(n) - 1] - '0'; ^ user.c:30:11: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(in, "%d", &t); ^ user.c:31:11: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(in, "%c" , &n[0]); ^ user.c:33:15: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(in, "%s", n); ^