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<string>
using namespace std;


int main(void){
	string org;
	getline(cin,org);

	for(int i=0; i<26; i++){
		for(int j=0; j<org.size(); j++){
			if( org[j] == '.' || org[j] == ' ' ) {}
			else {
				org[j]++;
				if( org[j] > 'z' )
					org[j] -= 26;
			}
		}
		string::size_type pos;
		pos = org.find("the");
		if( pos != string::npos ){
			cout << org << endl;
		}
		else{
			pos = org.find("this");
			if( pos != string::npos ){
				cout << org << endl;
			}
			else{
			pos = org.find("that");
			if( pos != string::npos ){
				cout << org << endl;
			}
			}
		}
	}
	return 0;
}

C++: #include <iostream>
#include <string.h>
#include <string>
#include <stdio.h>
using namespace std;
int main() {
	string w[3]={"the","this","that"},st;
	int wn[3]={3,4,4},k,i,j,s,f;
	while(getline(cin,st)) {
    k=0; 
	while(k<st.size()) {
		for (i=0;i<3;i++) {
			s=0; f=0;
			if (st.size()<k+wn[i]) break;
			for (j=0;j<wn[i]-1;j++) if (((w[i][j]-w[i][j+1]+26) % 26)==((st[k+j]-st[k+j+1]+26) % 26)) s++;
			if (s==wn[i]-1)  { f=1; i=5;}
		}
		if (f==1) break;
		for (k;st[k]>='a' && st[k]<='z' ; k++);
		k++;
	}
	if (f==0) cout << st; else {
		for (i=0;i<st.size();i++) 
			if ((st[i]>='a' && st[i]<='z')) cout << (char)(((st[i]-st[k]+'t')-97+26) % 26 + 97) ; 
		    else cout << st[i];
	}
	cout << endl;
	}
	return 0;
	}

C++: #include <iostream>
#include <cstdio>
#include <stdio.h>
#include <string.h>

using namespace std;
static const int MAXV = 81;

bool hantei(char* data);
void irekae(char* data);

int main() {
  while(!feof(stdin)) {
    char data[MAXV];
    if(fgets(data, sizeof(data), stdin)==NULL) break;
    while(!hantei(data))
      irekae(data);
    printf("%s", data);
  }
}

bool hantei(char* data) {
  if(strstr(data, "the")) return 1;
  if(strstr(data, "this")) return 1;
  if(strstr(data, "that")) return 1;
  return 0;
}

void irekae(char* data) {
  for(int i=0;data[i]!=0;i++) {
    if(data[i]>='a' && data[i]<='z') {
      if(data[i]=='z')data[i]='a';
      else data[i]++;
    }
  }
}

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

#define SIZE 3

using namespace std;

int main() {
	string str, value[SIZE] = {"the", "this", "that"};
	bool judge;
	while (getline(cin, str)) {
		judge = false;
		for (int i = 0; i < 25; i++) {
			for (int j = 0; j < str.size(); j++) {
				if ('a' <= str[j] && str[j] <= 'y') {
					str[j]++;
				}
				else if (str[j] == 'z') {
					str[j] = 'a';
				}
			}

			for (int j = 0; j < SIZE; j++) {
				if (str.find(value[j]) != str.npos) {
					judge = true;
				}
			}

			if (judge) {
				cout << str << endl;
				break;
			}
		}
	}

	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;
	char *tmp;
	is="this";e="the";at="that";
	tmp = strchr(s,is[0]);
	if(tmp==NULL) return false;
	while(tmp[0]!=NULL){
		if(!strncmp(tmp,is,4))	return true;
		if(!strncmp(tmp,e,4))	return true;
		if(!strncmp(tmp,at,3))	return true;
		tmp++;
	}
	return false;
}

C++: #include <bits/stdc++.h>
 
using namespace std;
 
#define FOR(i, j, k) for(int i = j; i < k; ++i)
#define rep(i, j) FOR(i, 0, j)
#define repr(i, j) for(int i = j; i >= 0; --i)
#define INF (1 << 30)
#define MOD 1e9 + 7
 
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> P;
 
int main() {
    string s;
    while(getline(cin, s)){
    	rep(i, 26) {
	    	rep(j, s.size()) {
	            if('a' <= s[j] && s[j] <= 'z') s[j] = s[j] + 'a';
	            else if(s[j] == 'z') s[j] = 'a';
	        }
	        if(s.find("the") != string::npos || s.find("this") != string::npos || s.find("that") != string::npos){
                cout << s << endl;
            }
	    }
    }
    return 0;
}

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

int main(){
  int str;
  string s;
  string tmp;
  getline(cin,s);
  for(int i=0;i<27;i++){
    for(int j=0;j<s.size();j++){
      if(s[j] >= 'a' && s[j] <= 'y') s[j]++;
      else if(s[j] == 'z') s[j]='a';
    }
      if((s.find("this")!=string::npos) || (s.find("that")!=string::npos) || (s.find("the")!=string::npos)) break;
    }
  cout << s << endl;
}

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

int main(){
  string in;
  int g = 0;
  getline(cin , in);
  while(1){
    string t[3] = {"the", "that", "this"};
    for(int j=0; j<3; j++)
      for(int i=0; i<4; i++)
      t[j][i] += g;
    
    if(in.find(t[0]) == string::npos ||
       in.find(t[1]) == string::npos ||
       in.find(t[2]) == string::npos
    ){
      g++; continue;
    } else break;
  }
  for(int i=0; i<in.size(); i++){
    char t = in[i];
    if(t == ' ' || t == '.' || t == ',')
      cout << t;
    else
      cout << (char)(in[i]-g);
  }
  cout << endl;
  return 0;
}

C++: #include<iostream>
#include<cstdio>
#include<string>
#include<sstream>
#include<vector>
using namespace std;
signed main(){
        char s[100];
        while( fgets(s, 100, stdin) != NULL ){
                vector<string> words;
                istringstream stream(s);
                string word;
                while(getline(stream, word, ' ')) words.push_back(word);
                int d;
                for(auto w: words){
                        if(w.length()==3 &&
                                        ((int)w[0] - (int)w[1] == (int)'t' - (int)'h') &&
                                        ((int)w[1] - (int)w[2] == (int)'h' - (int)'e')){
                                d = (int)w[0] -'t';
                                break;
                        }else if(w.length()==4 &&
                                        ((int)w[0] - (int)w[1] == (int)'t' - (int)'h') &&
                                        ((int)w[1] - (int)w[2] == (int)'h' - (int)'i') &&
                                        ((int)w[2] - (int)w[3] == (int)'i' - (int)'s')){
                                d = (int)w[0] -'t';
                                break;
                        }else if(w.length()==4 &&
                                        ((int)w[0] - (int)w[1] == (int)'t' - (int)'h') &&
                                        ((int)w[1] - (int)w[2] == (int)'h' - (int)'a') &&
                                        ((int)w[2] - (int)w[3] == (int)'a' - (int)'t')){
                                d = (int)w[0] -'t';
                                break;
                        }
                }
                for(unsigned int i=0; i<100 && s[i]!=0;i++){
                        char c=s[i];
                        if('a'<=c&&c<='z') printf("%c",(char)(c-d));
                        else printf("%c",c);
                }
        }
        return 0;
}