#include <stdio.h>

int main(void){
	int i,n;
	
	long long int c, d, sum=0;
	
	scanf("%d", &n);
	for(i=0;i<n;i++){
		scanf("%lld %lld", &c, &d); // c chair, d desk
		
		sum = sum + (((c+1)/2)%(1000000000+7) * (d%(1000000000+7)));
		sum = sum%(1000000000+7);
		
	}
	
	printf("%lld\n", sum);
	return 0;
}