#include <stdio.h>

int main(void)
{
	long n,c,d,s=0,i;
	scanf("%ld",&n);
	for(i=0;i<n;i++){
		scanf("%ld%ld",&c,&d);
		s+=(c+1)/2%100000007*d%1000000007;
	}
	printf("%ld",s);
	return 0;
}