#include <array>
#include <iostream>
#include <vector>

using namespace std;

int main() {
  int n;
  cin >> n;
  vector<array<int, 2>> v(n);
  for(auto& x: v) cin >> x[0] >> x[1];
  int ans = 0;
  while(true) {
    ans++;
    bool ret = true;
    for(auto [r, g]: v) {
      ret = ans % (r+g) >= r;
      if(!ret) {
        break;
      }
    }
    if(ret) {
      cout << ans << "\n";
      return 0;
    }
  }
}