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

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

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