#include <bits/stdc++.h>
using namespace std;
#define int long long
#define rep(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
template <class T>
bool chmax(T &a, const T& b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
template <class T>
bool chmin(T &a, const T& b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}


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