#include <fstream>
#include <cstdlib>
#include <cstdio>
#include <cmath>
using namespace std;
ifstream in("setb.in");
ofstream out("setb.out");
int aa[10001]={0};
int zs[200]={2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,101,103,107,109,113,
	127,131,137,139,149,151,157,163,167,173,179,181,191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271,277,281,
	283,293,307,311,313,317,331,337,347,349,353,359,367,373,379,383,389,397,401,409,419,421,431,433,439,443,449,457,461,463,
	467,479,487,491,499,503,509,521,523,541,547,557,563,569,571,577,587,593,599,601,607,613,617,619,631,641,643,647,653,659,
	661,673,677,683,691,701,709,719,727,733,739,743,751,757,761,769,773,787,797,809,811,821,823,827,829,839,853,857,859,863,
	877,881,883,887,907,911,919,929,937,941,947,953,967,971,977,983,991,997};
int main()
{
	int a,b,p;
	int ans=0;
	in>>a>>b>>p;
	for(int i=a;i<=b;i++)
	{
		for(int j=a;j<i;j++)
		{
			int k=0;
			while(1)
			{
				if(zs[k]>=i) break;
				if(i%zs[k]==0 && j%zs[k]==0 && zs[k]>=p)
				{
					if(aa[i]==0 && aa[j]==0)
					{
						ans++;
						aa[i]=aa[j]=ans;
						break;
					}else
					{
						if(aa[j]==0) aa[j]=aa[i];
						else  aa[i]=aa[j];
					}
				}
				k++;
			}
		}
	}
	for(int i=a;i<=b;i++)
	{
		if(aa[i]==0) ans++;
	}
	out<<ans<<endl;
    return 0;
}