Count Down Timer In C++

Question

How Can I use a count down timer in my code...?!!! Actually i wanna built a simple game in c++ & here is my code...

#include <cstdlib>
#include <ctime>
#include <iostream>

using namespace std;

int main()
{

srand((unsigned)time(0));
int x,y,z,a,i;
int ar[i];

x=(rand()%100);
cout<<"x = "<<x;
y=(rand()%100);
cout<<"\ny = "<<y;
z=x+y;
{
for (i=1;i<=5;i++)
{
cout<<"\nEnter Ur Answer = ";
cin>>ar[i];
if(z==ar[i])
{
cout<<"U R Correct";
exit(0);
}
else
cout<<"U R Wrong";
}
}
cout<<"\nCorrect answer is (x+y): "<<z;
return 0;
}