I had a class on C++ a few years ago and I am trying to brush up the little skills I have of this language. I am creating a program that lets you choose from 4 different games. When I choose a game to play it automatically goes to the first one no matter what game I choose. It also skips one of the programs and doesn't let me choose another after I chose the first game it just goes right to another. Can someone please help me?

#include <iostream>
#include <cstdlib>
using namespace std;

int choc;
int birth;
int sum;
int y;
int born;
int year_now, age_now, another_year, another_age;
int month, day, year, total;
int tries;
int guess;
int secret;
char again = 'y';
int games = 0;
int wins = 0;
int month_number;
int choice;
int main ()
{
cout << "Choose the game you wish to play:";
cout << endl;
cout << "1.Year " << "2.Chocolate " << "3.day born " << "4.guessing game ";
cout << endl;

cout << "Please enter your choice: "<< endl;
cout << endl;
int choice=0;
cin >> choice;
while (choice<1 && choice>=4)

if (choice == 1);

cout << "Enter the current year then press RETURN.\n";
cin >> year_now;

cout << "Enter your current age in years.\n";
cin >> age_now;

cout << "Enter the year for which you wish to know your age.\n";
cin >> another_year;

another_age = another_year - (year_now - age_now);
if (another_age >= 0) {
cout << "Your age in " << another_year << ": ";
cout << another_age << "\n";
}
else {
cout << "You weren't even born in ";
cout << another_year << "!\n";
}
cout << endl;

if (choice == 2);

cout << "Enter the year in which you were born. " << endl;
cin >> born;
cout << endl;
cout << "Pick the number of times you would like to have chocolate a week (more than one but less than ten)" << endl;
cin >> choc;
cout << endl;

sum = ((choc * 2) + 5) * 50;

cout << "Have you had your birthday this year? (y/n)" << endl;
cin >> birth;
cout << endl;

system("pause");
if (birth=='y'){
sum = sum + 1754;
}
else {
sum = sum + 1755;
}

sum = sum - born;

sum = sum +1;

cout << "The first digit is how many times you want chocolate, the last digits are your age." << endl;
cout << sum << endl;

if (choice == 3);

cout << "Enter your birth date, I will tell you\n";
cout << "the day of the week on which you were born.\n";

cout << "\nBirth date (mm dd yy): ";
cin >> month >> day >> year;

total = 0;

// divide the last two digits of the birth year by 4. Put in total.

total = total + ( year / 4 );

// add the last two digits of the birth year to total

total = total + year;

// add the last two digits of the birth date to total

total = total + day;

// find the month number

switch(month)
{
case 1:
case 10: month_number = 1;
break;
case 2:
case 3:
case 11: month_number = 4;
break;
case 4:
case 7: month_number = 0;
break;
case 5: month_number = 2;
break;
case 6: month_number = 5;
break;
case 8: month_number = 3;
break;
case 9:
case 12: month_number = 6;
break;
}

// ...and add it to total

total = total + month_number;

// if leap year and month is Jan or Feb, subtract 1 from total

if ( year % 4 == 0 && ( month == 1 || month == 2 ) )
total--;

// find the remainder when total is divided by 7

int remainder = total % 7;

// look up the remainder in the following table:

cout << "You were born on a ";

switch(remainder)
{
case 0: cout << "Saturday.\n";
break;
case 1: cout << "Sunday.\n";
break;
case 2: cout << "Monday.\n";
break;
case 3: cout << "Tuesday.\n";
break;
case 4: cout << "Wednesday.\n";
break;
case 5: cout << "Thursday.\n";
break;
case 6: cout << "Friday.\n";
break;
}

if (choice==4);

rand();

while ( again == 'y' )
{
games = games + 1;

cout << "I have picked a number between one and a hundred. ";
cout << "Try to guess it." << endl;
cout << "You lose if it takes you more than seven tries." << endl;
cout << endl;

secret = rand()% 100;
tries = 0;

while ( guess != secret )
{
tries = tries + 1;
cout << "Guess #" << tries << ": ";
cin >> guess;

if ( guess < secret )
cout << "Sorry, that's too low." << endl;
if ( guess > secret )
cout << "Sorry, that's too high." << endl;
} // while loop for each guess

cout << endl;
cout << "That's correct! You got it!" << endl;

if ( tries > 7 )
{
cout << "But it took you " << tries;
cout << " tries, so you lose." << endl;
}
else
{
cout << "And it only took you " << tries;
cout << " tries, so you win!" << endl;
wins = wins + 1;
}

cout << endl;
cout << "Play again? (y/n) ";
cin >> again;

// while loop for each game
}
cout << endl;
cout << "You played a total of " << games << " games." << endl;
cout << "You only guessed my number in seven tries or less ";
cout << wins << " times." << endl;
cout << "You are a foolish mortal." << endl;

return 0;
}