#include <stdio.h>
#define nsub 6
int main()
{
	int grade_pt[nsub], cred[nsub], i,gp_sum=0, cred_sum=0;
	float gpa;
	
	for (i=0; i<nsub; i++)
		scanf ("%d %d", &grade_pt[i],&cred[i]);

	for (i=0; i<nsub; i++)
	{
		gp_sum += grade_pt[i] * cred[i];

		cred_sum += cred[i];
	}
	gpa = (float) gp_sum / cred_sum;
	printf ("\n GPA is: %f\n", gpa);
}