#include<bits/stdc++.h>
using namespace std;
#define int long long 
const int INF = 1e9;
const int MOD = INF+7;
#define rep(i,N) for(int (i)=0;(i)<(N);++(i))
#define rrep(i,N) for(int (i)=(N-1);(i)>0;--i)
#define FOR(i,j,N) for(int (i)=(j);(i)<(N);++(i))
#define put(n) cout<<(n)<<endl;
#define all(v) v.rbegin(),v.rend()
#define MP make_pair
#define pb push_back
using P = pair<int,int>;

signed main(){
	int L,R,M;
	cin >> L >> R >> M;
	int ans;
	if((R - L + 1) / M) ans = M;
	else ans = (R - L + 1) % M;
	cout << ans << endl;
}