#include<iostream>
#include<algorithm>
using namespace std;
using lint=int64_t;

int main()
{
	lint L,R,M;

	cin >> L >> R >> M;
	
	lint LL=L%M;
	lint RR=R%M;
	if(RR-LL>=0)cout << RR-LL+1;
	else cout << M-LL+RR+1;
	cout << endl;
	return 0;
}