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<cstdio>
#include<string>
#include<iostream>
#include<algorithm>
using namespace std;

int caesar[26][255], x, enkrip[100];
int thiss[] = {'t', 'h', 'i', 's'}, the[] = {'t', 'h', 'e'}, that[] = {'t', 'h', 'a', 't'};
string s;
int main() {
	for(int i = 0; i <= 25; i++) {
		for(char j = 'a'; j <= 'z'; j++) {
			if(j + i > 'z') x = j + i - 26; else x = j + i;
			caesar[i][x] = j;
		}
	}
	while(getline(cin, s)) {
	for(int k = 0; k <= 25; k++) {
		int l = 0, z = 0, zz = 0;
		for(int i = 0, j = s.size(); i != j; i++) {
			if(s[i] <= 'z' && s[i] >= 'a') {
				enkrip[i] = caesar[k][s[i]];
				if(enkrip[i] == thiss[l]) l++;
				if(enkrip[i] == the[z]) z++;
				if(enkrip[i] == that[zz]) zz++;
			} else enkrip[i] = s[i];
		}
		if(l == 4 || z == 3 || zz == 4) {
			for(int i = 0, j = s.size(); i != j; i++) {
				printf("%c", enkrip[i]);
			}
			printf("\n");
			break;
		}
	}}
	return 0;
}

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

int main(){
	stirng s;
	while(getiline(cin,s)){
		while(s.find("the") == string::npos
				&& s.find("this") == string::npos
				&& s.find("that") == string::npos){
					for(int i = 0; i < s.size(): i++){
						if(s[i] == 'z')
							s[i] = 'a';
						else if(s[i] >= 'a' && s[i] <= 'z')
							s[i]++;
					}
				}
		cout << s << endl;		
	}
}

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 <math.h>

using namespace std;

int main(){

	char buf[81],result[81];
	bool FLG;
	short length;

	while(fgets(buf,81,stdin)!=0){
		FLG = false;
		length = 0;
		for(int i=0;buf[i]!='\0';i++)length++;
		for(int i=0;i<=25;i++){ //?????????????????°
			for(int k=0;buf[k]!='\0';k++){
				if(buf[k] >= 97 && buf[k] <= 122){
					if(buf[k]+i<=122){
						result[k]=buf[k]+i;
					}else{
						result[k]=97+(buf[k]+i-123);
					}
				}else{
					result[k]=buf[k];
				}
				result[k+1]='\0';
			}
			for(int k=0;result[k]!='\0';k++){
				// the this that ????????????????????????????????????
				if(length==4){
					if(result[0]=='t'&&result[1]=='h'&&result[2]=='e'&&result[3]=='.'){
						FLG=true;
						break;
					}
				}else{
					//??????
					if(result[0]=='t'&&result[1]=='h'&&result[2]=='e'&&result[3]==' '){
						FLG=true;
						break;
					}else if(result[0]=='t'&&result[1]=='h'&&result[2]=='i'&&result[3]=='s'&&result[4]==' '){
						FLG=true;
						break;
					}else if(result[0]=='t'&&result[1]=='h'&&result[2]=='a'&&result[3]=='t'&&result[4]==' '){
						FLG=true;
						break;
					}

					//????°?
					if(result[length-1]=='.'&&result[length-2]=='e'&&result[length-3]=='h'&&result[length-4]=='t'&&result[length-5]==' '){
							FLG=true;
							break;
					}
					if(length>5&&result[length-1]=='.'&&result[length-2]=='s'&&result[length-3]=='i'&&
							result[length-4]=='h'&&result[length-5]=='t'&&result[length-6]==' '){
							FLG=true;
							break;
					}else if(length>5&&result[length-1]=='.'&&result[length-2]=='t'&&result[length-3]=='a'&&
							result[length-4]=='h'&&result[length-5]=='t'&&result[length-6]==' '){
							FLG=true;
							break;
					}


					for(int p=4;result[p]!='\0';p++){
						if(result[p]==' ' && result[p-1] == 'e' && result[p-2] == 'h' && result[p-3] == 't' && result[p-4] == ' '){
							FLG = true;
							break;
						}
					}
					if(FLG)break;
					for(int p=5;result[p]!='\0';p++){
						if(result[p]==' ' && result[p-1] == 's' && result[p-2] == 'i' && result[p-3] == 'h' && result[p-4] == 't' && result[p-5] == ' '){
							FLG = true;
							break;
						}
					}
					if(FLG)break;
					for(int p=5;result[p]!='\0';p++){
						if(result[p]==' ' && result[p-1] == 't' && result[p-2] == 'a' && result[p-3] == 'h' && result[p-4] == 't' && result[p-5] == ' '){
							FLG = true;
							break;
						}
					}
					if(FLG)break;
				}
			}
			if(FLG)break;
		}
		printf("%s",result);

	}

    return 0;
}