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 <string>
using namespace std;
int n,m,l;
string s1, s2;
void input() {
	cin >> s1;
	if (s1 == ".")return;
	cin >> s2;
}
void output() {
	cout << endl;
}
void prep() {
	n = s1.length();
	m = s2.length();
	s1 = s1 + "$";
	s2 = s2 + "$";
}
void solve() {
	int i = 0;
	int j = 0;
	int h = 1;
	int cnt = 0;
	while (i+j<m+n-1) {
		h = 1 - h;
		string c1 = "";
		string c2 = "";
		while (i < n) {
			c1=c1+s1[i];
			if (s1[i] == '"')break;
			i++;
		}
		i++;
		while (j < m) {
			c2=c2+s2[j];
			if (s2[j] == '"')break;
			j++;
		}
		j++;
		if (c1._Equal(c2) == false) {
			if (h == 0) {
				cout << "DIFFERENT";
				return;
			}
			cnt++ ;
			if (cnt == 2) {
				cout << "DIFFERENT";
				return;
			}
		}
	}
	if (cnt == 0)cout << "IDENTICAL"; else cout << "CLOSE";
}
int main() {
	while (true) {
		input();
		if (s1 == ".")break;
		prep();
		solve();
		output();
	}
}

C++: #include <bits/stdc++.h>
using namespace std;

#define rep(i, n) for(int i = 0; i < (n); i++)
#define repp(i, l, r) for(int i = (l); i < (r); i++)
#define per(i, n) for(int i = ((n)-1); i >= 0; i--)
#define perr(i, l, r) for(int i = ((r)-1); i >= (l); i--)
#define all(x) (x).begin(),(x).end()
#define MOD 1000000007
#define IINF 1000000000
#define LINF 1000000000000000000
#define SP <<" "<<
#define CYES cout<<"Yes"<<endl
#define CNO cout<<"No"<<endl
#define CFS cin.tie(0);ios::sync_with_stdio(false)

typedef long long LL;
typedef long double LD;

int main(){
  while(1){
    string s;
    cin >> s;
    if(s==".") return 0;
    string t;
    cin >> t;
    vector<string> vs,vt;
    int pre=-1;
    rep(i,s.length()){
      if(s[i]=='"'){
        vs.push_back(s.substr(pre+1,i-pre-1));
        pre=i;
      }
    }
    vs.push_back(s.substr(pre+1,s.length()-pre-1));
    pre=-1;
    rep(i,t.length()){
      if(t[i]=='"'){
        vt.push_back(t.substr(pre+1,i-pre-1));
        pre=i;
      }
    }
    vt.push_back(t.substr(pre+1,t.length()-pre-1));
    int count = 0;
    if(vs.size()!=vt.size()){
      cout << "DIFFERENT" << endl;
      goto next;
    }
    for(int i=0;i<vs.size();i+=2){
      if(vs[i]!=vt[i]){
        cout << "DIFFERENT" << endl;
        goto next;
      }
    }
    for(int i=1;i<vs.size();i+=2){
      if(vs[i]!=vt[i]){
        count++;
      }
    }
    if(count==0){
      cout << "IDENTICAL" << endl;
    }else if(count==1){
      cout << "CLOSE" << endl;
    }else{
      cout << "DIFFERENT" << endl;
    }
    next:;
  }
  return 0;
}

C++: #include <algorithm>
#include <iostream>
#include <vector>
#include <math.h>
#include <set>
#include <map>
#include <string>
#include <stack>
#include <queue>
#include <iomanip>
#include <numeric>
#include <tuple>
#include <bitset>
#include <complex>
#include <unistd.h>
#include <cassert>
#include <cctype>
#include <random>
#define _USE_MATH_DEFINES
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> plglg;
typedef tuple<int, int, int> tiii;
typedef tuple<ll, ll, ll> tlglglg;
typedef complex<double> xy_t;
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};
double pi = 3.141592653589793;
ll mod = 1000000007;
int intmax = 2147483647;
int intmin = -2147483648;
ll llmax = 9223372036854775807;
ll llmin = -9223372036854775807;
ll inf = llmax / 2;
double eps = 1e-11;

int main() {
    while (true) {
        string s1, s2;
        cin >> s1;
        if (s1 == ".") {
            break;
        }
        cin >> s2;
        vector<char> s1ch[200];
        vector<char> s2ch[200];
        int num1 = 0;
        for (int i = 0; i < s1.size(); i++) {
            if (s1[i] == '"') {
                num1++;
            } else {
                s1ch[num1].push_back(s1[i]);
            }
        }
        int num2 = 0;
        for (int i = 0; i < s2.size(); i++) {
            if (s2[i] == '"') {
                num2++;
            } else {
                s2ch[num2].push_back(s2[i]);
            }
        }
        int mark = 0;
        if (num1 != num2) {
            mark = 2;
        }
        for (int i = 0; i <= num1; i++) {
            bool m = true;
            int a = s1ch[i].size();
            int b = s2ch[i].size();
            if (a != b) {
                m = false;
            } else {
                for (int j = 0; j < a; j++) {
                    if (s1ch[i][j] != s2ch[i][j]) {
                        m = false;
                    }
                }
            }
            if (!m) {
                if (i % 2 == 0) {
                    mark = 2;
                } else {
                    if (mark < 2) {
                        mark++;
                    }
                }
            }
        }
        if (mark == 0) {
            cout << "IDENTICAL" << endl;
        } else if (mark == 1) {
            cout << "CLOSE" << endl;
        } else {
            cout << "DIFFERENT" << endl;
        }
    }
}