#pragma GCC optimize("O3") #include <iostream> #include <iomanip> #include <cstdio> #include <string> #include <cstring> #include <deque> #include <list> #include <queue> #include <stack> #include <vector> #include <utility> #include <algorithm> #include <map> #include <set> #include <complex> #include <cmath> #include <limits> #include <cfloat> #include <climits> #include <ctime> #include <cassert> #include <numeric> #include <fstream> #include <functional> #include <bitset> using namespace std; using ll = long long; using P = pair<int, int>; using T = tuple<int, int, int>; template <class T> inline T chmax(T &a, const T b) {return a = (a < b) ? b : a;} template <class T> inline T chmin(T &a, const T b) {return a = (a > b) ? b : a;} constexpr int MOD = 1e9 + 7; constexpr int inf = 1e9; constexpr long long INF = 1e18; #define all(a) (a).begin(), (a).end() int dx[] = {1, 0, -1, 0}; int dy[] = {0, 1, 0, -1}; class UnionFind{ public: vector<int> par; vector<int> rank; vector<int> sz; int uf_size; UnionFind(int n){ par.resize(n); rank.resize(n); sz.resize(n); uf_size = n; for(int i=0; i<n; i++){ par[i] = i; rank[i] = 0; sz[i] = 1; } } int find(int x){ if(par[x] == x) return x; else return par[x] = find(par[x]); } bool same(int x, int y){ return find(x) == find(y); } bool unite(int x, int y){ x = find(x); y = find(y); if(x == y) return false; if(rank[x] < rank[y]) swap(x, y); if(rank[x] == rank[y]) rank[x]++; uf_size--; par[y] = x; sz[x] = sz[x] + sz[y]; return true; } int size(int x){ return sz[find(x)]; } }; int kruskal(int n, vector<T> &edge){ sort(edge.begin(), edge.end()); UnionFind uf(n); int res = 0; for(int i=0; i<edge.size(); i++){ int cost, cv, nv; tie(cost, cv, nv) = edge[i]; if(!uf.same(cv, nv)){ uf.unite(cv, nv); res += cost; } } return res; } int main(){ cin.tie(0); ios::sync_with_stdio(false); int l, r; cin>>l>>r; vector<T> edge; for(int i=l; i<=r; i++){ for(int j=i*2; j<=r; j+=i){ edge.emplace_back(0, i - l, j - l); } } for(int i=l; i<r; i++){ edge.emplace_back(1, i - l, i + 1 - l); } cout << kruskal(r - l + 1, edge) << endl; return 0; }