#include<bits/stdc++.h>
using namespace std;
long long a,b,p[100010],lp=0,mi[100010],d,z=0,ans=0,fa[100010];
bool bk[100010],ju[100010];
inline int find(int p){return fa[p]=(fa[p]==p)?p:find(fa[p]);}
int ddd(){
	freopen("setb.in","r",stdin);
	freopen("setb.out","w",stdout);
    scanf("%lld%lld%lld",&a,&b,&d);
    bk[1]=mi[1]=1;
    for(int i=2;i<=b;i++){
        if(!bk[i]){mi[i]=i;p[++lp]=i;}
        for(int j=1;j<=lp;j++){
		    if(p[j]*i>b)break;
		    bk[p[j]*i]=1;mi[i*p[j]]=mi[i];
		    if(i%p[j]==0)break;
		}
	}
	for(int i=1;i<=lp;i++){
	    if(p[i]<d&&p[i]>=a&&p[i]<=b)ans++;
	    if(p[i]>=d){z=i;break;}
	}
	for(int i=z;i<=lp;i++)fa[i]=i;
	for(int i=a;i<=b;i++)if(bk[i]&&mi[i]<d)ans++;
	for(int i=z;i<lp;i++){
	    for(int j=z+1;j<=lp;j++){
		    if(p[i]*p[j]>b)break;
		    if(a/(p[i]*p[j])<b/(p[i]*p[j])){
			    int f1=find(i),f2=find(j);
			    if(f1==f2)continue;
			    fa[f1]=f2;
			}
		}
	}
	for(int i=z;i<=lp;i++){
	    int f=find(i);
	    if(!ju[f])ans++,ju[f]=1;
	}
	printf("%lld",min(b-a+1,ans));
	return 0;
}
int yy=ddd();
int main(){;}