import std.conv, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.container, std.math, std.range, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) throw new EOFException; tokens = readln.split; } auto token = tokens[0]; tokens.popFront; return token; }
int readInt() { return readToken().to!int; }
long readLong() { return readToken().to!long; }
real readReal() { return readToken().to!real; }

void chmin(T)(ref T t, in T f) { if (t > f) t = f; }
void chmax(T)(ref T t, in T f) { if (t < f) t = f; }

int binarySearch(T)(in T[] as, in bool delegate(T) test) { int low = -1, upp = cast(int)(as.length); for (; low + 1 < upp; ) { int mid = (low + upp) >> 1; (test(as[mid]) ? low : upp) = mid; } return upp; }
int lowerBound(T)(in T[] as, in T val) { return as.binarySearch((T a) => (a < val)); }
int upperBound(T)(in T[] as, in T val) { return as.binarySearch((T a) => (a <= val)); }


Int gojo(Int)(Int a, Int b, out Int x, out Int y) {
  if (b != 0) { Int g = gojo(b, a % b, y, x); y -= (a / b) * x; return g; }
  x = 1; y = 0; return a;
}

// as[i] T == bs[i] (mod ms[i])
Tuple!(Int, "b", Int, "m") modSol(Int)(Int[] as, Int[] bs, Int[] ms) {
  Int B = 0, M = 1;
  foreach (i; 0 .. ms.length) {
    const a = as[i] % ms[i], b = bs[i] % ms[i];
    const b0 = b - a * B;
    Int x, y;
    const g = gojo(a * M, ms[i], x, y);
    if (b0 % g != 0) { B = M = 0; break; }
    const m0 = ms[i] / g;
    B += M * ((x * ((b0 / g) % m0)) % m0);
    M *= m0;
    B %= M;
  }
  if (B < 0) B += M;
  return Tuple!(Int, "b", Int, "m")(B, M);
}


immutable MO = 10L^^9 + 7;

int N;
BigInt[] X, Y;

void main() {
  try {
    for (; ; ) {
      N = readInt();
      X = new BigInt[N];
      Y = new BigInt[N];
      foreach (i; 0 .. N) {
        X[i] = readLong();
        Y[i] = readLong();
      }
      
      auto a = new BigInt[N];
      a[] = BigInt(1);
      auto res = modSol(a, X, Y);
      if (res.m == 0) {
        writeln(-1);
      } else {
        auto ans = res.b;
        if (ans == 0) {
          ans += res.m;
        }
        ans %= MO;
        writeln(ans);
      }
    }
  } catch (EOFException e) {
  }
}