Go: package main

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

var scanner = bufio.NewScanner(os.Stdin)

func nextString() string {
	scanner.Scan()
	return scanner.Text()
}

func incrementByte(b byte) byte {
	if b >= 97 && b < 122 {
		return b + 1
	} else if b == 122 {
		return 97
	}
	return b
}

func main() {
	scanner.Split(bufio.ScanLines)

	for {
		line := nextString()
		if len(line) == 0 {
			break
		}
		for i := 0; i <= 26; i++ {
			decoded := []byte{}
			for j := 0; j < len(line); j++ {
				decoded = append(decoded, incrementByte(line[j]))
			}
			line = string(decoded)
			if strings.Contains(line, "the") || strings.Contains(line, "this") || strings.Contains(line, "that") {
				fmt.Println(line)
				break
			}
		}
	}
}

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

typedef pair<string, string> P;

P next_word(string sentence) {
  if (sentence.empty()) return make_pair(string(""), string(""));
  if (sentence[0] == ' ' || sentence[0] == '.') {
    return make_pair("", sentence.substr(1));
  } else {
    P recur = next_word(sentence.substr(1));
    return make_pair(sentence[0] + recur.first, recur.second);
  }
}

bool acceptable(string sentence) {
  P p = next_word(sentence);

  while (! p.first.empty() ) {
    if (p.first == "this" || p.first == "the" || p.first == "that")
      return true;

    p = next_word(p.second);
  }
  return false;
}

char slip(char c) {
  if (c < 'a' || 'z' < c) return c;
  
  string alphabet = "abcdefghijklmnopqrstuvwxyza";
  int index = (int)(c - 'a');
  return alphabet[index + 1];
}

char slip(char c, int n) {
  for (int i = 0; i < n; i++)
    c = slip(c);

  return c;
}

string slip(string code, int n) {
  string val;
  for (int i = 0, len = code.length(); i < len; i++)
    val += slip(code[i], n);

  return val;
}

string decode(string code) {
  for (int i = 1; i < 27; i++) {
    string sentence = slip(code, i);
    if (acceptable(sentence))
      return sentence;
  }

  return "";
}

int main() {
  string code;
  while ( getline(cin, code) )
    cout << decode(code) << endl;
}

C++: #include <stdio.h>
#include <stdlib.h>
#include <algorithm>
#include <iostream>
#include <map>
#include <numeric>
#include <set>
#include <sstream>
#include <string>
#include <vector>
#include <cmath>
#include <string.h>
using namespace std;

#define FOR(i,s,e) for (int i = int(s); i != int(e); i++)
#define REP(i,e) for (int i = 0; i != int(e); i++)
#define FORIT(i, A) for (auto i : A)
#define ISEQ(c) (c).begin(), (c).end()
#define PRINT(x) cout << (x) << endl
#define SZ(x) ((int)(x).size())

#define DIST(a, b) (((a) - (b) + 26)%26)

int dht = DIST('h', 't');
int deh = DIST('e', 'h');
int dah = DIST('a', 'h');
int dta = DIST('t', 'a');
int dih = DIST('i', 'h');
int dsi = DIST('s', 'i');

int check(const char* word)
{
	if (DIST(word[1], word[0]) != dht)
		return -1;

	if (DIST(word[2], word[1]) == deh && 
		(word[3] == ' ' || word[3] == '\0' || word[3] == '\n'))
	{
		return DIST(word[0], 't');
	}
	if (DIST(word[2], word[1]) == dah && 
		DIST(word[3], word[2]) == dta &&
		(word[4] == ' ' || word[4] == '\0' || word[4] == '\n'))
	{
		return DIST(word[0], 't');
	}
	if (DIST(word[2], word[1]) == dih && 
		DIST(word[3], word[2]) == dsi && 
		(word[4] == ' ' || word[4] == '\0' || word[4] == '\n'))
	{
		return DIST(word[0], 't');
	}
	return -1;
}

int main(int argc, char const *argv[])
{
	string s;
	if (getline(std::cin, s))
	{
		int len = s.length();
		int d = check(&s[0]);
		int i = 3;
		while (d == -1)
		{
			while(i < len && s[i] != ' ')
				i++;
			if (i == len) break;
			i++;
			d = check(&s[i]);
		}
		REP(j, len)
		{
			if (s[j] >= 'a' && s[j] <= 'z')
			{
				s[j] = (s[j] - 'a' - d + 26) % 26 + 'a';
			}
		}
		std::cout << s << std::endl;
	}
	return 0;
}

C++: #include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
using namespace std;

int main(){

  int n;
  string s;
  int k;

  getline(cin,s);

  for(int i=-25;i<26;i++){
    bool d = false;
    for(int j=0;j<s.size();j++){
      if(s[j]+i == 't'){
	if(s[j+1]+i == 'h'){
	  if(s[j+2]+i == 'e') d = true;
	  if(s[j+3]+i == 'i' && s[j+4]+i == 's') d = true;
	  if(s[j+3]+i == 'a' && s[j+4]+i == 't') d = true;
	}
      }

      if(d == true){
	k = i;
	break;
      }

    }
  }

  for(int i=0;i<s.size();i++){
    if(s[i] >= 'a' && s[i] <= 'z') printf("%c",s[i]+k);
    else printf("%c",s[i]);
  }

  cout << endl;
}

C++: #include <iostream>
#include <string>
int main(int argc, const char * argv[])
{
    using namespace std;
    string word;
    int i;
    while (cin >> word) {
        for (i = 0; i < word.size(); i++) {
            if (isalpha(word[i])) {
                word[i] -= 4;
            }
        }
        cout << word;
        cout << " ";
    }
    cout << endl;
    return 0;
}

C++: #include <stdio.h>
#include <stdlib.h>
#include <string.h>
int caesar(char s[]);
bool search(char s[]);

int main(){
	char s[256];
	int i,j=0,n=10;
	while(scanf("%[^\n]",&s)!=EOF){
		while(!search(s)){
			for(i=0;s[i]!='.';i++){
				if(s[i]!=' ') s[i]++;
				if(s[i]>122) s[i]=97;
			}
		}
		printf("%s\n",s);
	}
	return 0;
}

bool search(char s[]){
	char *is,*e,*at;
	int i=0;
	char *tmp;
	is="this";e="the";at="that";
	while(s[i]!='.'){
		if(s[i]=='t'&&s[i+1]=='h'){
				if(s[i+2]=='e') return true;
				else if(s[i+2]=='i'&&s[i+3]=='s') return true;
				else if(s[i+2]=='a'&&s[i+3]=='t') return true;
		}
		i++;
	}
	return false;
}

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

using namespace std;

int main() {
	string str;
	string in;
	vector<string> s;
	//while (cin >> in) s.push_back(in);
	for (int i=0; i<(int)s.size(); i++) {
		str += s[i];
		if (i<(int)s.size()-1) str += " ";
	}
	
	str = "xlmw mw xli tmgxyvi xlex m xsso mr xli xvmt.";
	
	for (int i=0; i<26; i++) {
		if (str.find("the")!=str.npos || str.find("this")!=str.npos || str.find("that")!=str.npos) break;
		for (int j=0; j<(int)str.size(); j++) {
			if (str[j] == '.' || str[j] == ' ') continue;
			str[j] = 'a' + (str[j] - 'a' + 1)%26;
		}
	}
	
	cout << str << endl;
	
	return 0;
}

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

int main()
{
	string str;
	while(getline(cin,str)){
		int l,m;
		l = static_cast<int>(str[0] - 't');
		m = static_cast<int>(str[1] - 'h');
		if(l == m){
			for(unsigned i=0;i<str.size();i++){
				if(islower(str[i])){
					char c = static_cast<char>(static_cast<int>(str[i])-l);
					if(c<'a')
						c += 26;
					else if(c>'z')
						c-=26;
					cout << c;
				}else{
					cout << str[i];
				}
			}
			cout << endl;
		}
	}
	return 0;
}