#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
  #define _GLIBCXX_DEBUG
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

#include <atcoder/modint>
using mint = atcoder::modint1000000007;

int main() {
  int n;
  cin >> n;
  mint ans = 0;
  rep(_, n) {
    ll c, d;
    cin >> c >> d;
    ans += mint((c + 1) / 2) * d;
  }
  cout << ans.val() << endl;
  return 0;
}