/*#include <stdio.h>
int main()
{
int n, k, i,sum = 1;
scanf("%d", &n);
for(i = n; i>=1; i--)
{
sum =sum*i;
}
printf("%d", sum);
return 0;
}*/
/*#include <stdio.h>
int main()
{
int n, i, sum=0, a;
scanf("%d", &n);
for(i=1; i<=9; i++){
printf("%d*%d=%d\n", n,i, i*n);
}
return 0;
}*/
/*#include <stdio.h>
int main()
{
int n, i, sum=0;
scanf("%d", &n);
for(i=1; i<=n; i++){
if(i%2==0)
sum=sum+=i;
}
printf("%d", sum);
return 0;
}*/
#include <stdio.h>
int main()
{
int n, i, sum=0,a, b;
scanf("%d %d", &a, &b );
for(i=a; i<=b; i++){
if(i%2==0)
sum=sum+=i;
}
printf("%d", sum);
return 0;
}