Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

func main() {
	io := NewIo()
	defer io.Flush()
	for {
		s := io.NextLine()
		if s == "." {
			break
		}
		t := io.NextLine()
		if s == t {
			io.Println("IDENTICAL")
			continue
		}
		ss := strings.Split(s, "\"")
		tt := strings.Split(t, "\"")
		if len(ss) != len(tt) {
			io.Println("DIFFERENT")
			continue
		}
		cnt := 0
		for i := 0; i < len(ss); i++ {
			if i%2 == 0 {
				if ss[i] != tt[i] {
					cnt = -1
					break
				}
			} else {
				if ss[i] != tt[i] {
					cnt++
				}
			}
		}
		if cnt > 1 || cnt == -1 {
			io.Println("DIFFERENT")
		} else {
			io.Println("CLOSE")
		}
	}
}

// I/O template
type Io struct {
	reader    *bufio.Reader
	writer    *bufio.Writer
	tokens    []string
	nextToken int
}

func NewIo() *Io {
	return &Io{
		reader: bufio.NewReader(os.Stdin),
		writer: bufio.NewWriter(os.Stdout),
	}
}

func (io *Io) Flush() {
	err := io.writer.Flush()
	if err != nil {
		panic(err)
	}
}

func (io *Io) NextLine() string {
	var buff []byte
	for {
		line, isPrefix, err := io.reader.ReadLine()
		if err != nil {
			panic(err)
		}
		buff = append(buff, line...)
		if !isPrefix {
			break
		}
	}
	return string(buff)
}

func (io *Io) Next() string {
	for io.nextToken >= len(io.tokens) {
		line := io.NextLine()
		io.tokens = strings.Fields(line)
		io.nextToken = 0
	}
	s := io.tokens[io.nextToken]
	io.nextToken++
	return s
}

func (io *Io) NextInt() int {
	i, err := strconv.Atoi(io.Next())
	if err != nil {
		panic(err)
	}
	return i
}

func (io *Io) NextFloat() float64 {
	i, err := strconv.ParseFloat(io.Next(), 64)
	if err != nil {
		panic(err)
	}
	return i
}

func (io *Io) Println(a ...interface{}) {
	fmt.Fprintln(io.writer, a...)
}

func (io *Io) Printf(format string, a ...interface{}) {
	fmt.Fprintf(io.writer, format, a...)
}

func (io *Io) PrintIntSlice(a []int) {
	b := []interface{}{}
	for _, x := range a {
		b = append(b, x)
	}
	io.Println(b...)
}

func (io *Io) PrintStringSlice(a []string) {
	b := []interface{}{}
	for _, x := range a {
		b = append(b, x)
	}
	io.Println(b...)
}

func Log(name string, value interface{}) {
	fmt.Fprintf(os.Stderr, "%s=%+v\n", name, value)
}

func ExampleIo() {
	io := NewIo()
	defer io.Flush()
	a := make([]int, 0, 3)
	a[0], a[1], a[2] = io.NextInt(), io.NextInt(), io.NextInt()
	io.Println(a)
	io.PrintIntSlice(a)
	Log("io", a)
}

C++: #include <iostream>
#include <iomanip>
#include <cstdio>
#include <string>
#include <cstring>
#include <deque>
#include <list>
#include <queue>
#include <stack>
#include <vector>
#include <utility>
#include <algorithm>
#include <map>
#include <set>
#include <complex>
#include <cmath>
#include <limits>
#include <cfloat>
#include <climits>
#include <ctime>
#include <cassert>
#include <numeric>
#include <fstream>
#include <functional>
#include <bitset>
#define chmin(a, b) ((a)=min((a), (b)))
#define chmax(a, b) ((a)=max((a), (b)))
#define fs first
#define sc second
#define eb emplace_back
using namespace std;

typedef long long ll;
typedef pair<int, int> P;
typedef tuple<int, int, int> T;

const ll MOD=1e9+7;
const ll INF=1e18;
const double pi=acos(-1);
const double eps=1e-10;

int dx[]={1, 0, -1, 0};
int dy[]={0, -1, 0, 1};

vector<string> calc(string s){
    vector<string> v;
    int pre = 0;
    int cnt = 1;
    for(int i=0; i<s.size(); i++){
        if(s[i] == '\"'){
            string t = s.substr(pre, i - pre + 1);
            if(cnt % 2){
                v.eb(t);
            }
            else{
                v.eb(t);
            }

            pre = i;
            cnt++;
        }
    }

    return v;
}

int main(){
    while(1){
        string s1; cin>>s1;
        if(s1 == ".") return 0;
        string s2; cin>>s2;

        if(s1 == s2){
            cout << "IDENTICAL" << endl;
            continue;
        }

        auto ans1 = calc(s1);
        auto ans2 = calc(s2);        

        int dif = 0;
        for(int i=0; i<ans1.size() && i<ans2.size(); i++){
            if(i % 2 == 0){
                if(ans1[i] != ans2[i]) dif = 2;
            }
            else{
                if(ans1[i] != ans2[i]) dif++;
            }
        }

        if(dif == 1){
            cout << "CLOSE" << endl;
        }
        else{
            cout << "DIFFERENT" << endl;
        }
    }
}

C++: #include<iostream>
#include<string>
#include<vector>

using namespace std;

void split(string &s, vector<string> &v) {
	s += '"';
	string buf = "";
	for (int i = 0; i < s.size(); i++) {
		if (s[i] == '"') {
			v.push_back(buf);
			buf = "";
		}
		else buf += s[i];
	}
}

int main() {

	while (1) {
		string S1, S2;
		cin >> S1;
		if (S1 == ".")break;
		cin >> S2;
		//すでに完全に一致ならば
		if (S1 == S2) {
			cout << "IDENTICAL" << endl;
			continue;
		}
		vector<string> v1, v2;
		split(S1, v1), split(S2, v2);

		if (v1.size() != v2.size()) {
			cout << "DIFFERENT" << endl;
			continue;
		}
		
		int cnt = 0;
		for (int i = 0; i < v1.size(); i++) {
			if (i % 2 == 0) {
				if (v1[i] != v2[i]){
					cout << "DIFFERENT" << endl; cnt++;
					continue;
				}
			else {
				if (v1[i] != v2[i]) {
					cnt++;
				}
			}
		}
		if (cnt > 1) {
			cout << "DIFFERENT" << endl;
		}
		else {
			cout << "CLOSE" << endl;
		}
	}
	
	return 0;
}

C++: #include <iostream>
#include <cmath>
#include <utility>
#include <functional>
#include <math.h>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <string>
#include <set>
#include <map>
#include <tuple>
#include <stdlib.h>
#include <deque>
using namespace std;
#define rep(i,n,x) for(int i=n;i<x;i++)
#define rem(i,n,x) for(int i=n;i>x;i--)
#define SORT(x) sort(x.begin(),x.end())
#define REV(x) reverse(x.begin(),x.end())
#define all(x) x.begin(),x.end()
#define pb push_back
#define mp make_pair
#define setp(x) setprecision(x)
using LL = long long;
using ULL = unsigned long long;

int main() {
	string s1, s2;
	cin >> s1 >> s2;

	while (s1 != ".") {
		string ans = "DIFFERENT";
		// s1とs2が一致
		if (s1 == s2) ans = "IDENTICAL";
		// s1とs2が惜しいかを判定
		else {
			bool counter = true;
			rep(i,0,200) {
				string S1 = "", S2 = "";
				// " "内の処理 " "の中身をS1,S2に入れ、s1,s2から削除
				if (s1[i] == '"' && s2[i] == '"') {
					int j = i + 1;
					while (s1[j] != '"') {
						S1 += s1[j];
						s1.erase(s1.begin() + j);
					}
					while (s2[j] != '"') {
						S2 += s2[j];
						s2.erase(s2.begin() + j);
					}
					i = j;
				}
				// " "外で異なる文字列があればループを抜ける
				else if (s1[i] != s2[i]) break;
				// ""内の文字が異なればCLOSE(1回目)
				if (S1 != S2) {
					ans = "CLOSE";
					counter = false;
					break;
				}
			}
			// ""内の文字が異なればDIFFERENT(2回目)
			if (!counter && s1 != s2) ans = "DIFFERENT";
		}
		
		cout << ans << endl;

		cin >> s1 >> s2;
	}

	return 0;
}

C++: #include <bits/stdc++.h>

using namespace std;

int main(){
    string s,t;
    while(true){
        cin>>s;
        if(s==".")break;
        cin>>t;
        int errcnt=0;
        int sind=0,tind=0;
        while(sind<s.size()&&tind<t.size()){
            if(s[sind]!=t[tind]){
                errcnt=2019;
                break;
            }
            if(s[sind]=='"'){
                ++sind;++tind;
                while(s[sind]!='"'||t[tind]!='"'){
                    if(s[sind]!=t[tind]){
                        ++errcnt;
                        while(s[sind]!='"')++sind;
                        while(t[tind]!='"')++tind;
                        break;
                    }
                    ++sind;++tind;
                }
            }
            if(errcnt>=2)break;
            ++sind;
            ++tind;
        }
        if(sind==s.size()&&tind!=t.size())errcnt=2019;
        if(tind==t.size()&&sind!=s.size())errcnt=2019;
        if(errcnt==0)cout<<"IDENTICAL"<<endl;
        else if(errcnt==1)cout<<"CLOSE"<<endl;
        else cout<<"DIFFERENT"<<endl;
    }
    return 0;
}