#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <math.h>
int main(void)
{
    long int kindofdesk,chair,desk,ppl=0,mod=1000000007;
    scanf("%ld",&kindofdesk);
    for(int i=0;i<kindofdesk;i++)
    {
        scanf("%ld %ld",&chair,&desk);
        chair=(chair+1)/2%mod;
        desk%=mod;
        ppl+=chair*desk;
        ppl%=mod;
    }
    printf("%d",ppl);
}