Go: package main

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

var scanner = bufio.NewScanner(os.Stdin)

func cipher(text string, direction int, int_shift int) string {
	shift, offset := rune(int_shift), rune(26)
	runes := []rune(text)
	for index, char := range runes {
		switch direction {
		case 1:
			if char >= 'a' && char <= 'z'-shift || char >= 'A' && char <= 'Z'-shift {
				char = char + shift
			} else if char > 'z'-shift && char <= 'z' || char > 'Z'-shift && char <= 'Z' {
				char = char + shift - offset
			}
		case -1:
			if char >= 'a'+shift && char <= 'z' || char >= 'A'+shift && char <= 'Z' {
				char = char - shift
			} else if char >= 'a' && char < 'a'+shift || char >= 'A' && char < 'A'+shift {
				char = char - shift + offset
			}
		}
		runes[index] = char
	}
	return string(runes)
}

func main() {
	for scanner.Scan() {
		infos := strings.Split(scanner.Text(), " ")
		plain := make([]string, len(infos))
		// fmt.Println(infos)
		Decryption:
			for i := 0; i < 26; i++ {
				for j := range infos {
					plain[j] = cipher(infos[j], 1, i)
				}
				for j := range plain {
					if plain[j] == "this" || plain[j] == "that" || plain[j] == "the" {
						break Decryption
					}
				}
			}
			fmt.Println(strings.Join(plain, " "))
	}
}

C++: #include<iostream>
#include<list>
#include<string>
#include<cctype>
using namespace std;

bool checkString(int* key, string s);
void rotateChar(string* s, int i);

int main()
{
    list<string> table;
    char text[80];
	int size=0;

	for(size=0; cin.get(text[size]); size++ ){;}

	char ch;
	string s;
	for(int i=0; (ch=text[i])!=EOF; i++){
		if(ch!=' ')s.push_back(ch);
		else{ table.push_back(s), s.clear();}
	}		

    int key; // ずらす文字数
    list<string>::iterator i;
    for(i=table.begin(); i!=table.end(); i++){
        // cout << *i << " ";
        if( i->size() == 3 || i->size() == 4 )
            if( checkString(&key, *i) ) break;
    }
	
	for(int i=0; i<size; i++){
		char ch = text[i];
		if(isalpha(ch)){
        char c = ch - 'a';
        ch = 'a' + (c+key)%26;
		}
		cout.put(ch);
	}

    return 0;
}

void rotateChar(string* s, int i) // iは何文字ずらしたいか
{

    for(int j=0; j<s->size(); j++){
        if(!isalpha(s->at(j))){continue;}
        char c = s->at(j) - 'a';
        s->at(j) = 'a' + (c+i)%26;
    }
}

bool checkString(int* key, string s)
{

    for(int i=0; i<26; i++){
        string tmp = s;
        rotateChar(&tmp, i);
        // cout << tmp << endl;
        if( tmp=="the" || tmp=="this" || tmp=="that" ){
            *key=i;
            return true;
        }
    }
    return false;
}

C++: #include <fstream>
#include <iostream>
#include <cmath>
#include <vector>
#include <queue>
#include <utility>
#include <algorithm>
using namespace std;

char shift(char c, int n) {
  if (c >= 'a' && c <= 'z')
    return (c + n <= 'z') ? c + n : 'a' + (c + n - 'z' - 1);
  else
    return c;
}

bool exist(string str, string c) {
  return str.find(c, 0) != string::npos;
}

int main() {
  // ifstream cin("../test.txt");
  vector<string> _the(26);
  vector<string> _this(26);
  vector<string> _that(26);
  _the[0] = "the";
  _this[0] = "this";
  _that[0] = "that";
  for (int i = 1; i < 26; i++) {
    for (int j = 0; j < 3; j++) {
      _the[i] += shift(_the[0][j], i);
    }
    for (int j = 0; j < 4; j++) {
      _this[i] += shift(_this[0][j], i);
      _that[i] += shift(_that[0][j], i);
    }
  }

  string str, nstr;
  // 復号化
  while (getline(cin, str)) {
    if (str.length() == 0) break;
    nstr = "";
    for (int i = 1; i < 26; i++) {
      if ( exist(str, _the[i]) || exist(str, _this[i]) || exist(str, _that[i])) {
        int len = str.length();
        for (int j = 0; j < len; j++) {
          nstr += shift(str.at(j), 26 - i);
        }
        break;
      }
    }

    cout << nstr << endl;
  }
  // 暗号化
  // while (getline(cin, str)) {
  //   for (int i = 1; i < 26; i++) {
  //     nstr = "";
  //     int len = str.length();
  //     for (int j = 0; j < len; j++) {
  //       nstr += shift(str[j], i);
  //     }
  //     cout << nstr << endl;
  //   }
  // }
}

C++: #include<bits/stdc++.h>
using namespace std;
void Caesarcipher(string &s,int c){
  if(c<0) c = 26+c%26;
  else c %= 26;
  for(int i=0;i<s.size();i++){
    if('a' <= s[i] && s[i] <= 'z'){
      s[i] += c;
      if(s[i] > 'z') s[i] -= 26;
      else if(s[i] < 'a') s[i] += 26;
    }
  }
}
int main(){
  string s;int i;
  while(getline(cin,s)){
    for(i=0;i<26;i++){
      Caesarcipher(s,1);
      if(s.find("the") != string::npos || s.find("this") != string::npos || s.find("that") != string::npos){
        cout << s << "\n";
      }
    }
  }
}

C++: #include <bits/stdc++.h>
using namespace std;
#define FOR(i, s, n) for(int i = s; i < (int)n; i++)
#define per(i, n) for(int i = n; i >= 0; i--)
#define ROF(i, s, n) for(int i = s; i >= (int)n; i--)
#define FORIT(i, A) for (auto i : A)
#define PRINT(x) cout << (x) << "\n"
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define MP make_pair
#define EACH(i, n) for (__typeof((n).begin()) i = (n).begin(); i != (n).end(); ++i)
#define SZ(a) int((a).size())
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())
#define CLR(a) memset((a), 0 ,sizeof(a))
#define NCLR(a) memset((a), -1 ,sizeof(a))
#define dump(x) cout << #x << " = " << (x) << "\n";
#define debug(x) cout << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << "\n";
#define sq(n) (n) * (n)
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;
typedef vector<LL> VLL;
typedef vector<VLL> VVLL;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef priority_queue<int> maxpq;
typedef priority_queue< int, vector<int>, greater<int> > minpq;
typedef complex<double> P;
static const double EPS = 1e-10;
static const double PI = acos( -1.0 );
static const int mod = 1000000007;
static const int INF = 1 << 30;
static const LL LL_INF = 1152921504606846976;
static const int dx[] = { -1, 0, 1, 0, 1, -1, 1, -1 };
static const int dy[] = { 0, -1, 0, 1, 1, 1, -1, -1 };

string str;
map<char, char> change;

int main() {
	for ( int i = 0; i < 26; i++ ) {
		change[ i + 'a' ] = ( i + 25 ) % 26 + 'a';
	}
	while ( getline( cin, str ) ) {
		for ( ;; ) {
			for ( int j = 0; j < str.size(); j++ ) {
				if ( str[ j ] >= 'a' && str[ j ] <= 'z' ) {
					str[ j ] = change[ str[ j ] ];
				}
			}
			bool is_can = false;
			for ( int j = 2; j < str.size(); j++ ) {
				if ( str.substr( j - 2, 3 ) == "the" ) {
					is_can = true;
					break;
				}
			}
			for ( int j = 3; j < str.size(); j++ ) {
				if ( str.substr( j - 3, 4 ) == "that" || str.substr( j - 3, 4 ) == "this" ) {
					is_can = true;
					break;
				}
			}
			if ( is_can ) {
				break;
			}

		}
		printf( "%s\n", str.c_str() );
	}
	return 0;
}

C++: #include<stdio.h>
#include<string.h>
int main(void){
    int i,j,k;
    char input[100],cpyinput[100],key[3][5]={"the","this","that"};
    while(gets(input)!=NULL){
        for(i=0;i<26;i++){
            for(j=0;j<strlen(input);j++){
                if('a'<=input[j] && input[j]<='z'){
                    input[j]+=1;
                    if(input[j]>'z')
                        input[j]-=26;
                }
                //printf("%c",input[j]);
            }
            //puts("");
            //printf("%s\n",input);
            //puts("test");
            for(j=0;j<3;j++){
                if(strstr(input,key[j])!=NULL){
                    //printf("test");
                    goto next;
                }
            }
        }
        next:
        printf("%s\n",input);
    }
    return 0;
}