#include<iostream>
int getin(double* a1, int* a2,int m);
int main() {
	int n = 0;
	std::cin >> n;
	if (n > 5000) return -1;
	double* a = new double[n];
	int* t = new int[n];
   //读取数据然后决定灯的长度
	int k = getin(a, t, n);
	int* lamp = new int[k+1];
   //数组0号位不用
	for (int i = 1; i < k+1; i++) {
		lamp[i] = 0;
	}
	for (int i = 0; i < n; i++) {
		for (int j = 1; j <= t[i]; j++) {
			int x = int(a[i] * j);
			if (!lamp[x]) lamp[x] = 1;
			else lamp[x] = 0;
		}
	}
	for (int i = 1; i < k + 1; i++) {
		if (lamp[i]) {
			std::cout << i;
			break;
		}
	}
	return 0;
}
int getin(double* a1, int* a2,int m) {
	int x = 0;
	for (int i = 0; i < m; i++) {
		std::cin >> a1[i] >> a2[i];
		if (x<int(a1[i] * a2[i])) {
        //找a*t的最大值也就是最后一盏灯用来			//决定灯的数量
			x = int(a1[i] * a2[i]);
		}
	}
	return x;
}