#include <iostream>
#include <iomanip>

typedef long long ll;

int main(void)
{
  std::cin.tie(0);
  std::ios::sync_with_stdio(false);
  std::cout << std::fixed << std::setprecision(3);
  ll n;
  std::cin >> n;
  ll ans = 0;
  for (ll i = 0; i < n; ++i) {
    ll c, d;
    std::cin >> c >> d;
    ans = (ans + (c+1)/2 * d) % 1000000007;
  }
  std::cout << ans << std::endl;
  return 0;
}