(fgets(text,MAX_LEN,stdin)==NULL)exit(EXIT_FAILURE);len=strlen(text);if(text[len-1]=='\n')text[len-1]='\0';len-=1;printf("Choose shift number [1-26]: ");fflush(stdout);if(fgets(num,16,stdin)==NULL)exit(EXIT_FAILURE);shift=(int)strtol(num,NULL,0);if(shift<1||shift>...