#include <stdio.h>

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