Go: package main

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

var scanner = bufio.NewScanner(os.Stdin)

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

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 {
		infos := strings.Split(nextString(), " ")
		plain := make([]string, len(infos))
		if len(infos) == 0 {
			break
		}
		// 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 <string>

using namespace std;

int main()
{
  string stro, str;
  while(getline(cin, stro)){
    for(int i = 0; i < 26; i++){
      str = stro;
      for(int j = 0; j < stro.length(); j++){
	if(str[j] >= 'a' && str[j] <= 'z')
	  if(str[j] + i > 'z')
	    str[j] += i - 26;
	  else
	    str[j] += i;
      }
      std::string::size_type f_the = str.find("the", 0);
      std::string::size_type f_this = str.find("this", 0);
      std::string::size_type f_that = str.find("that", 0);
      if((f_the != string::npos && f_the == 0 && (str[f_the + 3] == ' ' || str[f_the + 3] == '.' || str[f_the + 3] == '\0')) || (f_this != string::npos && f_this == 0 && (str[f_this + 4] == ' ' || str[f_this + 4] == '.' || str[f_this + 4] == '\0')) || (f_that != string::npos && f_that == 0 && (str[f_that + 4] == ' ' || str[f_that + 4] == '.' || str[f_that + 4] == '\0')))
	cout << str << endl;
      else if((f_the != string::npos && (str[(f_the - 1 < 0) ? 0 : f_the - 1] == ' ' || str[(f_the - 1 < 0) ? 0 : f_the - 1] == '.' || str[(f_the - 1 < 0) ? 0 : f_the - 1] == '\n') && (str[f_the + 3] == ' ' || str[f_the + 3] == '.' || str[f_the + 3] == '\0')) || (f_this != string::npos && (str[(f_this - 1 < 0) ? 0 : f_this - 1] == ' ' || str[(f_this - 1 < 0) ? 0 : f_this - 1] == '.' || str[(f_this - 1 < 0) ? 0 : f_this - 1] == '\n') && (str[f_this + 4] == ' ' || str[f_this + 4] == '.' || str[f_this + 4] == '\0')) || (f_that != string::npos && (str[(f_that - 1 < 0) ? 0 : f_that - 1] == ' ' || str[(f_that - 1 < 0) ? 0 : f_that - 1] == '.' || str[(f_that - 1 < 0) ? 0 : f_that - 1] == '\n') && (str[f_that + 4] == ' ' || str[f_that + 4] == '.' || str[f_that + 4] == '\0')))
	cout << str << endl;	 
    }
  }
}

C++: #include <stdio.h>
int check(int a,int b,int c,int d)
{
    //printf("[%d][%d][%d][%d]\n",a,b,c,d);
    if(a != 14)return 0;
    else if(b == 23 && c == 0)return 1;
    else if(b == 1 && c == 10 && d == 0)return 1;
    else if(b == 19 && c == 19 && d == 0)return 1;
    else return 0;
}

int main()
{
    int longth,mem;
    while(1)
    {
        char str[90] = {0};
        int mem1[90] = {0},mem2[90] = {0};
        if(scanf("%c",&str[0]) == -1)return 0;
        if(str[0] >= 'a' && 'z' >= str[0])mem1[0] = str[0] - 'a' + 1;
        for(int i = 1; i < 80; i++)
        {
            scanf("%c",&str[i]);
            if(str[i] == '\n')break;
            longth = i;
            if(str[i] >= 'a' && 'z' >= str[i])mem1[i] = str[i] - 'a' + 1;
        }
        for(int i = 0; i < longth; i++)
        {
            if(mem1[i] == 0);
            else if(mem1[i + 1] != 0)
            {
                if(mem1[i] <= mem1[i + 1])mem2[i] = mem1[i + 1] - mem1[i];
                else mem2[i] = 26 - mem1[i] + mem1[i + 1];
            }
        }
        /*for(int i = 0; i < longth; i++)
        {
            printf("[%d]",mem2[i]);
        }
        printf("\n");*/
        for(int i = 0; i < longth; i++)
        {
            if(mem2[i] == 0);
            else if(i == 0)if(check(mem2[i],mem2[i + 1],mem2[i + 2],mem2[i + 3]))/*printf("%d\n",i);*/if(mem1[i] <= 20)mem = 20 - mem1[i];else mem = 26 - mem1[i] + 20;
            else if(mem2[i - 1] != 0)if(check(mem2[i],mem2[i + 1],mem2[i + 2],mem2[i + 3]))/*printf("%d\n",i);*/if(mem1[i] <= 20)mem = 19 - mem1[i];else mem = 26 - mem1[i] + 20;
        }
        //printf("{%d}\n",mem);
        for(int i = 0; i < longth + 1; i++)
        {
            if(str[i] >= 'a' && 'z' >= str[i])printf("%c",(str[i] - 'a' + mem) % 26 + 'a');
            else printf("%c",str[i]);
        }
        printf("\n");
    }
}

C++: #include<cstdio>
#include<iostream>
#include<cstring>

using namespace std;
int key;

int dist(char s1,char s2){
 
  if(s1==s2){
    return 0;
  }else if(s1<s2){
    return s2-s1;
  }else{
    return 'z'-s1+s2-'a'+1;
  }
}

bool checkThe(char s[]){
  if(strlen(s)!=3){
    return false;
  }else{
    if(dist('t',s[0])==dist('h',s[1]) && dist('h',s[1])==dist('e',s[2])){
      key=dist('t',s[0]);
      return true;
    }
  }
  return false;
}
bool checkThis(char s[]){
  if(strlen(s)!=4){
    return false;
  }else{
    if(dist('t',s[0])==dist('h',s[1]) && dist('h',s[1])==dist('i',s[2]) && dist('i',s[2])==dist('s',s[3])){
      key=dist('t',s[0]);
      return true;
    }
  }
  return false;
}
bool checkThat(char s[]){
  if(strlen(s)!=4){
    return false;
  }else{
    if(dist('t',s[0])==dist('h',s[1]) && dist('h',s[1])==dist('a',s[2]) && dist('a',s[2])==dist('t',s[3])){
      key=dist('t',s[0]);
      return true;
    }
  }
  return false;

}
int main(){
 
  char str[100];
  char temp[100];
 
  char *tok;
  bool f;
  while(fgets(str,sizeof(str),stdin)!=NULL){
    key=0;
    f=false;
    for(int i=0;i<strlen(str);i++)
      temp[i]=str[i];
    temp[strlen(str)]='\0';

    str[strlen(str)]='\0';
    str[strlen(str)-1]='\0';
    tok=strtok(str," ");
 
    if(strlen(tok)==3){
      if(checkThe(tok)==true){
	f=true;
      }
    }else if(strlen(tok)==4){
      if(checkThat(tok)==true){
	f=true;
      }else if(checkThis(tok)==true){
	f=true;
      }
    }
    while(f==false && tok!=NULL){
      tok=strtok(NULL," ");
      if(tok!=NULL){
	if(strlen(tok)==3){
	  if(checkThe(tok)==true){
	    f=true;
	  }
	}else if(strlen(tok)==4){
	  if(checkThat(tok)==true){
	    f=true;
	  }else if(checkThis(tok)==true){
	    f=true;
	  }
	}
      }
    }
 
   
    for(int i=0;i<strlen(temp);i++){
      if('a'<=temp[i] && temp[i]<='z'){
	if(temp[i]-key>'z'){
	  printf("%c",(temp[i]-key));
	}else if(temp[i]-key<'a'){
	  printf("%c",(temp[i]-key)+26);
	}else{
	  printf("%c",(temp[i]-key));
	}
      }else{
	printf("%c",temp[i]);
      }
    }

  }

  return 0;
}