#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
#define pb push_back
#define mp make_pair
#define rep(i,n) for(int i=0;i<(n);++i)
const int mod=1000000007;

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	int l,r,m;cin >> l >> r >> m;
	if(l/m==r/m){
		cout << r%m-l%m+1 << endl;
	}
	else if(r/m-l/m==1){
		if(r%m>=l%m) cout << m << endl;
		else cout << m-l%m+r%m+1 << endl;
	}
	else{
		cout << m << endl;
	}
}