#include <algorithm> #include <cmath> #include <cstdio> #include <vector> using namespace std; using i64 = long long; constexpr int MOD = 1e9 + 7, INV_2 = 500000004; #define SQ(X) ((i64)(X) * (X)) inline int add(int x, int y) { return (x + y + MOD) % MOD; } template <class T> inline int mul(T x, T y) { return (i64)(x % MOD) * (y % MOD) % MOD; } inline int div_2(int x) { return mul(x, INV_2); } inline int sum(i64 l, i64 r) { return div_2(mul(l + r, r - l + 1)); } int main() { // freopen("alice.in", "r", stdin); // freopen("alice.out", "w", stdout); i64 l, r; vector<i64> left, right; vector<bool> sgn; scanf("%lld %lld", &l, &r); int mem = sqrt(r) - sqrt(l) + 5; left.reserve(mem); right.reserve(mem); sgn.reserve(mem); for (int i = sqrt(l); SQ(i) <= r; ++i) { i64 lst = SQ(i - 1), curr = SQ(i), nxt = SQ(i + 1); left.emplace_back(curr - ((curr - lst) >> 1)); right.emplace_back(curr + ((nxt - curr) >> 1)); sgn.emplace_back(curr & 1); } int ans = 0, len = sgn.size(); for (int i = 0; i < len; ++i) { i64 lo = left[i], hi = right[i]; int sign = sgn[i] ? 1 : -1; if (hi < l || lo > r) continue; lo = max(lo, l); hi = min(hi, r); ans = add(ans, sign * sum(lo, hi)); } printf("%d\n", ans); return 0; }