#include <iostream>
#include <set>
using namespace std;

typedef long long LL;
int main(int argc, char* argv[])
{
	LL L,R,M,i;
	cin>>L>>R>>M;
	if (L==R){
		cout<<1<<endl;
		return 0;
	}
	set<LL> mySet;
	for (i=L;i<=R;i++){
		mySet.insert(i%M);
	}
	cout<<mySet.size()<<endl;
	return 0;
}