Go: package main

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

var scanner = bufio.NewScanner(os.Stdin)

func main() {
	for scanner.Scan() {
		var result string
		line := scanner.Text()
		key := make(map[string]string)

		var i int32
		for ; i < 52; i++ {
			makeKey(key, i)
			result = decode(key, line)

			if strings.Contains(result, "the") {
				break
			} else if strings.Contains(result, "this") {
				break
			} else if strings.Contains(result, "that") {
				break
			}
		}

		fmt.Println(result)
	}
}

func makeKey(key map[string]string, shift int32) {
	for i := 'a'; i <= 'z'; i++ {
		cipher := (i + shift)
		if cipher > 'z' {
			cipher = cipher%'z' + 'a' - 1
		} else if cipher < 'a' {
			cipher = cipher + ('z' - 'a') + 1
		}
		key[string(i)] = string(cipher)
	}
}

func decode(key map[string]string, cipher string) string {
	var result string
	for _, v := range cipher {
		if key[string(v)] != "" {
			result += key[string(v)]
		} else {
			result += string(v)
		}
	}
	return result
}

C++: #include <string>
#include <vector>
#include <algorithm>
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <queue>
#include <map>
#define INF 100000000

using namespace std;
typedef long long ll;

string change(string s){
    int len=s.size();
    for(int i=0;i<len;i++){
        if('b'<=s[i] && s[i]<='z')s[i]--;
        if(s[i]=='a')s[i]='z';
    }
    return s;
}

bool check(string s){
    int len=s.size();
    string tan="";
    for(int i=0;i<len;i++){
        if('a'<=s[i] && s[i]<='z'){
            tan+=s[i];
        }
        else{
            if(tan=="the" || tan=="this" || tan=="that" )return true;
            tan="";
        }
    }
    return false;
}


int main(){
    string s;
    getline(cin,s);
    for(int i=0;i<26;i++){
        s=change(s);
        if(check(s)){cout<<s<<endl;return 0;}
    }
    
    return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <cmath>
#include <vector>
#include <deque>
#include <list>
#include <string>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <algorithm>
#include <stdio.h>

using namespace std;

int pat[3][3];
int len[3];
int chr[3];
int zure;
int size;
bool atteru[3];
char text[100];

int main() {
	//cin >> text;
	gets(text);
	//int size = text.size();
	int pt = 0;
	size = 100;

	pat[0][0] = 't' - 'h';
	pat[0][1] = 'h' - 'e';
	pat[1][0] = 't' - 'h';
	pat[1][1] = 'h' - 'i';
	pat[1][2] = 'i' - 's';
	pat[2][0] = 't' - 'h';
	pat[2][1] = 'h' - 'a';
	pat[2][2] = 'a' - 't';
	chr[0] = 'e';
	chr[1] = 's';
	chr[2] = 't';
	len[0] = 3;
	len[1] = 4;
	len[2] = 4;

	for (int i = 0; i < 3; i++) {
		for (int j = 0; j < 3; j++) {
			if (pat[i][j] < 0) pat[i][j] += 26;
		}
	}

	zure = -1;

	int cnt = 0;
	atteru[0] = true;
	atteru[1] = true;
	atteru[2] = true;
	for (int i = 0; i < size-1 && zure == -1; i++) {
		if (text[i] == ' ') {
			cnt = 0;
			atteru[0] = true;
			atteru[1] = true;
			atteru[2] = true;
			//cout << "yarinaoshi!" << endl;
			continue;
		}
		if (text[i+1] == ' ' || cnt > 3) continue;
		int dist = text[i] - text[i+1];
		if (dist < 0) dist += 26;
		for (int j = 0; j <= 2; j++) {
			if (!atteru[j]) continue;
			if (cnt >= len[j]-1) continue;
			if (dist != pat[j][cnt]) {
				atteru[j] = false;
				//cout << j << " ha tigau!" << endl;
				continue;
			} else if (cnt == len[j]-2) {
				if (text[i+2] == ' ') {
					//cout << j << " ha atteta!" << endl;
					zure = text[i+1] - chr[j];
					if (zure < 0) zure += 26;
					//cout << "zure = " << zure << endl;
				} else {
					atteru[j] = false;
					continue;
				}
			}
		}
		cnt++;
	}

	for (int i = 0; i < size; i++) {
		if (text[i] == EOF) break;
		if (text[i] < 'a' || text[i] > 'z') continue;
		text[i] = text[i] - zure;
		if (text[i] < 'a') text[i] += 26;
	}

	cout << text << endl;

	return 0;
}

/*@@@@@@@@@@@@@@@@@@@@@@@@@*/
/*@                       @*/
/*@ debug output erased ? @*/
/*@                       @*/
/*@@@@@@@@@@@@@@@@@@@@@@@@@*/

C++: #include<iostream>
#include<string>
#include<sstream>
#include<vector>
using namespace std;
#define REP(i, j) for(int i = 0; i < j; i++)
#define FOR(i, j, k) for(int i = j; i < k; i++)
const int N = 26;

bool isOK(vector<string> v){
    REP(i, v.size()) if(v[i] == "the" || v[i] == "this" || v[i] == "that") return true;
    return false;
}

int main(){
    string str;
    while(getline(cin, str)){
        str = str.substr(0, str.size() - 1);
        REP(pls, N){
            string tmp;
            stringstream ss(str);
            vector<string> ans;
            while(ss >>tmp){
                REP(i, tmp.length()) tmp[i] = 'a' + ((tmp[i] - 'a'  + pls) % N);
                ans.push_back(tmp);
            }
            if(isOK(ans)){
                cout <<ans[0];
                FOR(i, 1, ans.size()) cout <<" " <<ans[i];
                cout <<'.' <<endl;
                break;
            }
        }
    }
    return 0;
}

C++: 

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cmath>
#include<math.h>
#include<string>
#include<string.h>
#include<stack>
#include<queue>
#include<vector>
#include<utility>
#include<set>
#include<map>
#include<stdlib.h>
#include<iomanip>

using namespace std;

#define ll long long
#define ld long double
#define EPS 0.0000000001
#define INF 1e9
#define MOD 1000000007
#define rep(i,n) for(i=0;i<n;i++)
#define loop(i,a,n) for(i=a;i<n;i++)
#define all(in) in.begin(),in.end()
#define shosu(x) fixed<<setprecision(x)

typedef vector<int> vi;
typedef pair<int,int> pii;

int main(void) {
  int i,j,k;
  string s;
  while(getline(cin,s)){
    int n=0;
    rep(i,s.size())if(s[i]==' ')n++;
    n++;
    vector<string> word(n);
    i=0;
    rep(j,n){
      while(s[i]>='a' && s[i]<='z')
	word[j].push_back(s[i]),i++;
      i++;
    }
    rep(k,26){
      bool c=false;
      rep(i,n)rep(j,word[i].size())
	if(word[i][j]=='z')word[i][j]='a';
	else word[i][j]=word[i][j]+1;
      rep(i,n)
	if(word[i]=="the" || word[i]=="this" || word[i]=="that"){
	  c=true;break;
	}
      if(c){
	rep(i,n){
	  if(i)cout<<" ";
	  cout<<word[i];
	}
	cout<<"."<<endl;
	break;
      }
    }
  }
}

C++:  
 #include<iostream>
 #include<stdio.h>
 #include<string>
 #include<math.h>
 #include<iomanip>
 #include<algorithm>
 #include<string.h>
 #include<cctype>
 #include<map>
 #include<set>
 #include<vector>
 #include<sstream>
 #include<stack>
 
 using namespace std;
  
 int main()
 {
   string a,b;
   while(getline(cin,a))
   {
     for(int shift=0;shift<26;shift++)
     {
       b="";
       for(int i=0;i<a.length();i++)
       {
         if(a[i]>='a'&&a[i]<='z')
         { 
           if(a[i]+shift>'z') b+=(a[i]+(shift-26));
           else b+=(a[i]+shift);
         }         
         else b+=a[i]; 
       }
       if(b.find("the")!=string::npos||b.find("this")!=string::npos||b.find("that")!=string::npos) break;
       else continue;
     }             
     cout<<b<<endl;
   }
   //while(1);      
   return 0;    
 }

C++: #include <cstdio>
#include <cstdlib>
#include <iostream>
#include <string>
#include <cmath>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <map>

using namespace std;
typedef long long ll;

int main(){
    int in;
    char S[1000];
    
    gets(S);
    
    while(1){
        
        bool f = false;
        
        for(int i=0;S[i]!='\0';i++){
            if('a'<=S[i] && S[i]<='y'){
                S[i]++;
            }else if(S[i]=='z'){
                S[i]='a';
            }
            
            if(i>=2){
                if(S[i-2]=='t' && S[i-1]=='h' && S[i]=='e')
                    f=true;
            }
            if(i>=3){
                if(S[i-3]=='t' && S[i-2]=='h')
                    if((S[i-1]=='i' && S[i]=='s') || (S[i-1]=='a' && S[i]=='t'))
                        f=true;
            }
        }
        
        if(f) break;
    }
    
    printf("%s\n",S);
    
    return 0;
}