#include<bits/stdc++.h>
using namespace std;
inline int read()
{
	char ch=getchar();int x=0,fa=1;
	while(ch<'0'||ch>'9'){if(ch=='-')fa=-1;ch=getchar();}
	while(ch>='0'&&ch<='9'){x=x*10-48+ch;ch=getchar();}
	return x*fa;
}
const int maxn=100005;
int a,b,c,q[maxn],qwq[maxn],tot;
int fa[maxn],prime[maxn],cnt,x,ans;
bool check[maxn];
int getfa(int x)
{
	if(fa[x]==x)return x;
	else return fa[x]=getfa(fa[x]);
}
void u(int x,int y)
{
	fa[getfa(x)]=getfa(y);
}
void Euler(int n)
{
	check[1]=1;
	for(int i=2;i<=n;i++)
	{
		if(!check[i])prime[++cnt]=i;
		for(int j=1;j<=cnt&&i*prime[j]<=n;j++)
		{
			check[i*prime[j]]=1;
			if(i%prime[j]==0)break;
		 } 
	} 
}
int main()
{
	freopen("setb.in","r",stdin);
	freopen("setb.out","w",stdout);
	a=read(),b=read(),c=read();
	Euler(b);
	for(int i=a;i<=b;i++)fa[i]=i;
	for(int i=c;i<=b;i++)
	{
		if(!check[i])qwq[++tot]=i;
	}
	for(int i=1;i<=tot;i++)
	{
		x=0;
		while(x*qwq[i]<a)x++;
		while((x+1)*qwq[i]<=b)
		{
			u(qwq[i]*x,qwq[i]*(x+1));
			x++;
		}
	}
	for(int i=a;i<=b;i++)if(fa[i]==i)ans++;
	cout<<ans;
	return 0;
}