#include<stdio.h>
#define K 1000000007

int main(void){
	unsigned long long int n,c,d,r=0,i;
	scanf("%llu",&n);
	for(i = 1;i <= n;i++){
		scanf("%llu%llu",&c,&d);
		if(c%2){c = (c+1)/2;}else{c/=2;}
		r+=(((c%K)*(d%K))%K);
		r%=K;
	}
	printf("%llu\n",r);
	return 0;
}