#define _USE_MATH_DEFINES #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include typedef long long int ll; //#include using namespace std; int gcd(int a, int b) { if (a < b)swap(a, b); if (b == 0)return a; return gcd(b, a % b); } int lcm(int a, int b) { return a * b / gcd(a, b); } int main() { int Q; Q = 1; //cin >> Q; while (Q--) { ll n; cin >> n; ll mod = 1000000007; long long ans = 0; for (int i = 0; i < n; i++) { ll c, d; cin >> c >> d; if (c % 2 == 0) { ans += (c / 2) % mod * (d % mod) % mod; } else { ans += (c / 2 + 1) % mod * (d % mod) % mod; } ans %= mod; } cout << ans%mod; } return 0; }