#include<stdio.h>
int main()
{
	int a,b;
	scanf("%d%d",&a,&b);
	printf("%.1f",(a-1)*2.5+b*1.5);
	return 0;
}
/**************************************************************
	Problem: 1603
	User: admin
	Language: C
	Result: Accepted
	Time:10 ms
	Memory:1144 kb
****************************************************************/