#include<bits/stdc++.h>
#define ll long long
#define uint unsigned int
using namespace std;
int const N=1e6+10;
int f[N],pr[N],v[N];
int a,b,p,m=0;
void primes(int n)
{
    for(int i=2;i<=n;++i) v[i]=1;
    for(int i=2;i<=n;++i)
    {
        if(!v[i]) continue;
        pr[++m]=i;
        for(int j=i;j<=n/i;++j) v[i*j]=0;
    }
    return;
}
void init()
{
    for(int i=a;i<=b;i++) f[i]=i;
    return;
}
int get(int x)
{
    if(x==f[x]) return x;
    return f[x]=get(f[x]);
}
void merge(int x,int y)
{
    int fx=get(x),fy=get(y);
    if(fx!=fy) f[fy]=fx;
    return;
}
int main()
{
    freopen("setb.in","r",stdin);
    freopen("setb.out","w",stdout);
    
    cin>>a>>b>>p;
    init();
    primes(b);
    for(int i=1;i<=m;i++)
    {
        if(pr[i]<p) continue;
        int t=1;
        bool flag=false;
        while(t*pr[i]<=b)
        {
            if(t*pr[i]<a) t++;
            else
            {
                if(flag) merge(t*pr[i],(t-1)*pr[i]);
                else flag=true;
                t++;
            }
        }
    }
    int ans=0;
    for(int i=a;i<=b;i++) if(i==f[i]) ans++;
    cout<<ans<<endl;
    return 0;
}