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 <cstdio>
#include <vector>
using namespace std;
typedef pair<int,char*> str;

int main(void){
	char s[81];
	vector<str> v;
	const char* cmp1="that";
	const char* cmp2="this";
	const char* cmp3="the";
	bool is_found=false;
	int pos=0,end_pos,diff;
	char c;

	scanf("%[^\n]",s);
	for(int i=0;i<81;i++){
		if(s[i]==' ' || s[i]=='.'){
			c=s[i];
			s[i]='\0';
			v.push_back(str(i-pos,s+pos));
			s[i]=c;
			pos=i+1;
		}else if(s[i]=='\0'){
			end_pos=i;
			break;
		}
	}

	for(int i=0;i<v.size();i++){
		is_found=false;

		diff=1000;
		if(v[i].first==4){
			for(int j=0;j<4;j++){
				if(diff==1000){
					diff=v[i].second[j]-cmp1[j];
				}else if(diff!=v[i].second[j]-cmp1[j]){
					is_found=true;
					break;
				}
			}

			if(!is_found) break;

			diff=1000;
			for(int j=0;j<4 && !is_found;j++){
				if(diff==1000){
					diff=v[i].second[j]-cmp2[j];
				}else if(diff!=v[i].second[j]-cmp2[j]){
					is_found=true;
					break;
				}
			}

			if(!is_found) break;
		}else if(v[i].first==3){
			diff=1000;
			for(int j=0;j<3;j++){
				if(diff==1000){
					diff=v[i].second[j]-cmp2[j];
				}else if(diff!=v[i].second[j]-cmp2[j]){
					is_found=true;
					break;
				}
			}
			if(!is_found) break;
		}
	}
	
	for(int i=0;i<end_pos;i++){
		if(s[i]!=' ' && s[i]!='.'){
			s[i]-=diff;
		}
	}

	printf("%s\n",s);


	return 0;
}

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

char buf[1000];
string enc, ans;

string decrypt(string s, int k) {
  string ret = "";
  for (int i=0; i<s.size(); i++) {
    char c = s[i];
    if ('a' <= c && c <= 'z') {
      ret += ('a' + ((c-'a')+k)%26);
    } else {
      ret += c;
    }
  }
  return ret;
}

int main() {
  while (1) {
    if (fgets(buf, 100, stdin) == NULL) break;
    enc = buf;
    for (int i=0;i<26;i++) {
      ans = decrypt(enc, i);
      if (ans.find("the") != string::npos) break;
      if (ans.find("this") != string::npos) break;
      if (ans.find("that") != string::npos) break;
    }

    printf("%s", ans.c_str());
  }
}

C++: #include<iostream>
#include<cstring>
#include<stdio.h>
using namespace std;

int main(){
  char a[100],b[100];
  for(int i;i<100;i++){
    a[i]='\0';
    b[i]='\0';
  }
  gets(a);
  int i=0;
  while(i<26){
    for(int j=0;!(a[j]=='\0');j++){
      if(0x61<=a[j]+i&&a[j]+i<=0x7A)
	b[j]+=i;
      else if(0x61<=a[j]&&a[j]<=0x7A){
	b[j]=a[j]-26+i;
      }
      else if(a[j]==' ')
	b[j]=' ';
      else if(a[j]=='.')
	b[j]='.';
      
    }
    if(strstr(b,"the")||strstr(b,"this")||strstr(b,"that"))
      break;
    i++;
  }
  for(int k=0;a[k]!='\0';k++)
    cout<<b[k];
  cout<<'\n';
  return 0;
}

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

using namespace std;

int main()
{
	string str;
	
	while (getline(std::cin, str), !str.empty()){
		int j = 0;
		int di = 0;
		bool flag = false;
		for (int i = 0; i < str.size(); i++){
			if (str[i] == ' '){
				if (i - j < 5 && i - j > 1){
					if (str[j] - str[j + 1] == 12){
						if (str[j + 1] - str[j + 2] == 3){
							di = str[j] - 't';
							flag = true;
							break;
						}
						else if (str[j + 1] - str[j + 2] == -1){
							if (str[j + 2] - str[j + 3] == -10){
								di = str[j] - 't';
								flag = true;
								break;
							}
						}
						else if (str[j + 1] - str[j + 2] == 7){
							if (str[j + 2] - str[j + 3] == -19){
								di = str[j] - 't';
								flag = true;
								break;
							}
						}
					}
					
				j = i + 1;
				}
			}
		}
		
		for (int i = 0; i < str.size();i++){
			if ('a' <= str[i] && str[i] <= 'z'){		
				str[i] = str[i] - di;
			}
		}
		if (flag){
			cout << str << endl;
		}
	}
}

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

string arrs[200];

bool judge4(const string &str) {
	int d1 = str[0] - 't';
	int d2 = str[1] - 'h';
	int d3 = str[2] - 'i';
	int d4 = str[3] - 's';
	int d5 = str[2] - 'a';
	int d6 = str[3] - 't';
	return (d1 == d2 && ((d2 == d3 && d3 == d4) || (d2 == d5 && d3 == d6)));
}

bool judge3(const string &str) {
	int d1 = str[0] - 't';
	int d2 = str[1] - 'h';
	int d3 = str[2] - 'e';
	return (d1 == d2 && d2 == d3);
}

int main() {
	cin.clear();
	int cnt = 0;
	while (!cin.eof()) {
		cin >> arrs[cnt++];
		char ch = getchar();
		if (ch == '\n') {
			bool isOk = 0;
			int delta = 0;
			for (int i = 0; i < cnt; ++i) {
				if (arrs[i].length() == 4) {
					if (judge4(arrs[i])) {
						isOk = 1;
						delta = arrs[i][0] - 't';
						break;
					}
				}else if (arrs[i].length() == 3) {
					if (judge3(arrs[i])) {
						isOk = 1;
						delta = arrs[i][0] - 't';
						break;
					}
				}
			}
			for (int i = 0; i < cnt; ++i) {
				for (int j = 0; j < arrs[i].length(); ++j) 
					if (arrs[i][j] != '.') arrs[i][j]-= delta;
				cout << arrs[i] << ((i == cnt - 1) ? "\n" : " ");
			}
			cnt = 0;
		}
	}
	return 0;
}

C++: #include<iostream>
#include<string>
#define num 27
using namespace std;

int main(){
	int i;
	string str;
	getline(cin, str);
	string strcp = str;
	string::iterator si;
	for(i=0;i<num;i++){
		if(  strcp.find("this") != string::npos
		  || strcp.find("that") != string::npos
		  || strcp.find("the" ) != string::npos){
			cout << strcp << endl;
		}
		si = strcp.begin();
		while(si != strcp.end()){
			if('a' <= *si && *si <= 'y'){
				*si = *si + char(1);
			}else if(*si == 'z'){
				*si = 'a';
			}
			si++;
		}
	}
	return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <regex>
using namespace std;

vector<string> v;

vector<string> split(string&& s, regex&& pattern) {
    sregex_token_iterator first(s.begin(), s.end(), pattern, -1);
    sregex_token_iterator last;
    return(vector<string>(first, last));
}

bool cheser() {
    for(int r = 1; r <= 50; r++) {
        bool found = false;
        for(int c = 0; c < v.size(); c++) {
            for(int k = 0; k < v[c].length(); k++) {
                if(!isalpha(v[c][k])) continue;
                int now = v[c][k] - 'a';
                now = (now+1)%26;
                v[c][k] = 'a' + now;
            }
            if(v[c] == "the" || v[c] == "this" || v[c] == "that") found = true;
        }
        if(found) return(true);
    }
    return(false);
}

int main(void) {
    string input;
    while(getline(cin, input)) {
        v = split(move(input), regex(" "));
        cheser();
        for(int r = 0; r < v.size(); r++) {
            cout << v[r];
            if(r == v.size() - 1) cout << endl;
            else                  cout << " ";
        }
    }
    
    return(0);
}

C++: #include<iostream>
#include<string>
using namespace std;
int main(){
  int ans=-1,len=0;
  string s;
  while(getline(cin,s)){
    while(1){
      ans = s.find("the");
      if(ans!=-1)break;
      ans = s.find("this");
      if(ans!=-1)break;
      ans = s.find("that");
      if(ans!=-1)break;
      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;
  }
}