Compilare: user.c: In function ‘main’: user.c:15:1: warning: implicit declaration of function ‘strlen’ [-Wimplicit-function-declaration] len = strlen(number); ^ user.c:15:7: warning: incompatible implicit declaration of built-in function ‘strlen’ [enabled by default] len = strlen(number); ^ user.c:17:5: warning: implicit declaration of function ‘isdigit’ [-Wimplicit-function-declaration] if(isdigit(number[i])){ ^ user.c:12:7: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(file1, "%d %d", &B, &K); ^ user.c:13:7: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(file1, "%s", number); ^