PRIME1 SIGSEGV error

[ilidek]

Hi I found that Sieve of Atkin is much faster than Sieve of Eratosthenes anyway something don't work and I have time like 1 minute. Can you help me improve my program a bit? I am not sure what's wrong and how can I make it work faster.

#include <iostream>
#include <cmath>
using namespace std;
int main()
  {
   const long unsigned limit = 1000001;         
   bool Tb[limit]={false};
   Tb[2]=Tb[3]=true;
   unsigned root=sqrt(limit-1);
   for(unsigned x=1;x<root;++x)
     for(unsigned y=1;y<root;++y)
       {
        unsigned N=(4*x*x)+(y*y);
        if((N<=limit)&&((N%12==1)||(N%12==5)))Tb[N]=true;
        N=(3*x*x)+(y*y);
        if((N<=limit)&&((N%12==7)))Tb[N]=true;
        N=(3*x*x)-(y*y);
        if((x>y)&&(N<=limit)&&(N%12==11))Tb[N]=true;
       }
   for(unsigned N=5;N<root;++N)  
      if(Tb[N])
        {
         for(unsigned n=1, k=2;n<root;++k)
           {
            n=N*k;
            Tb[n]=false;
           }
        }
   unsigned T;
   cin>>T;
   while(T--)
     {
      unsigned n,m;
      cin>>n>>m;
      while(n<=m)
        {
         if(Tb[n])cout<<n<<endl;
         ++n;
        }
     }
   cin.get();
   return 0;
  }