uva 406 bt binary

#include<stdio.h>
#include<iostream>
#include<bits/stdc++.h>
using namespace std;
#define M 1010
int nprime=0;
bool mark[M];

vector<int>prime;

void primegen()
{
    int i,j;

    mark[1]=false;

    mark[2]=false;

    prime.push_back(1);
    nprime++;
    prime.push_back(2);
    nprime++;
    for(i=3;i<=1001;i+=2)
    {
        if(mark[i]==false)
        {
            prime.push_back(i);
            nprime++;
        }
        for(j=i*i;j<=1001;j+=2*i)
        {
            mark[j]=true;
        }
    }

   }


void myfunc(int n,int k,int c)
{

    int i;
     if(n==c)
    {
         printf("%d %d: ",n,c);
        for(i=0;prime[i]<=n;i++)
            printf("%d ",prime[i]);

        cout<<endl;
            return ;
    }
    else if(k%2==0)
    {
        int count=0;
        printf("%d %d: ",n,c);
        for(i=(k/2-c)+1; ;i++)
        {
            printf("%d ",prime[i-1]);
           count++;
        if(count==2*c)
        {
            printf("\n");
            break;
        }
        }

    }
    else
    {
        int count=0;
        printf("%d %d: ",n,c);
        for(i=k/2-c+1; ;i++)
        {
            printf("%d ",prime[i]);
            count++;
            if(count==2*c-1)
            {
                cout<<endl;
                break;
            }

        }

    }
}
int binary(int n)
{
    int high,low,mid;
    high=prime.size()-1;
    low=0;
    while(high>=low)
    {
        mid=(high+low)/2;
        if(prime[mid]<=n  && prime[mid+1]>n) return mid;
        else if(prime[mid]>n)
        {
            high=mid-1;
        }
        else
        {
            low=mid+1;
        }

    }
}

int main()
{
    int n,c,k;
    primegen();
    while(scanf("%d %d",&n,&c) && n!=EOF)
    {
        k=1+binary(n);
        myfunc(n,k,c);
    }


    return 0;
}