Why is my code of finding and listing all prime numbers from 1 to z (where z is the input number) not working?

Question

#include <iostream>
using namespace std;

int main()
{
int i,a,z;
cin>>z;

for(a=2;a<=z;a++)
{

for (i=1;i<=a;i++)
{
if (a%i==0)
{
z++;
}
}
if (z==2)
cout<<a<<endl;
}
return 0;
}

Answer 1

because you are incrementing the input variable and never reset it ^^

corrected code to keep your logic:

#include <iostream>
using namespace std;

int main()
{
int i,a,z,f;
cin>>z;

for(a=2;a<=z;a++)
{

for (f=0,i=1;i<=a;i++)
{
if (a%i==0)
{
f++;
}
}
if (f==2)
cout<<a<<endl;
}
return 0;
}

Answer 2

visph Thank you for the correction. It works perfectly now!