#include <bits/stdc++.h> using namespace std; int main() { int a, b; cin >> a >> b; vector<long long> sum(b+1); for (int i = 2; i <= b; i++) { for (int j = i+i; j <= b; j += i) sum[j] += i; sum[i]++; } long long ans = 0; for (int i = a; i <= b; i++) ans += abs(i-sum[i]); cout << ans << '\n'; return 0; }