PROGRAM TO FIND PRIME NOS IN C++

//PROGRAM TO FIND PRIME NOS IN C++
#include<iostream.h>
void main()
{
int a;
cout<<"Enter a no"<<endl;
cin>>a;

int s=0;
for(int i=1;i<a;i++)
{
if(a%i==0)
{
s=1;
}
else
{
s=0;
}
}
if(s==1)
cout<<"no is prime";
else
cout<<"no is nt prime";
}