#include<stdio.h>
int main(void)
{
    int x,y,i,t;
    int sum = 0;
    scanf("%d",&x);
    scanf("%d",&y);
    if(x > y)
    {
        t = x;
        x = y;
        y = t;
    }
    for(i = x + 1;i < y; i++){
        if(i % 2 != 0){
            sum = sum + i;
        }
    }
    printf("%d",sum);
    return 0;
}