#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>



int main(int argc, char *argv[])
{

	int N = 0;
	scanf("%u", &N);

	unsigned long long lC = 0;
	unsigned long long lD = 0;
	unsigned long long lE = 0;
	unsigned long long mod = 1000000000 + 7;

	for (int i = 0; i < N; i++)
	{
		scanf("%llu %llu", &lC, &lD);

		if (lC % 2 == 0)
			lE += ( lC / 2 ) % mod * ( lD % mod ) % mod;
		else
			lE += ( lC / 2 + 1 ) % mod * ( lD  % mod ) %mod;
	}
	printf("%llu\n", lE % mod);

	return 0;

}