#include<iostream>
#include<cstdio>
using namespace std;
int main(){
int x,y;
cin >> x >> y;
int sum = 0;
if(x > y){
x = x - 1;
for(;x>y;x--){
if(x%2 == 0){
continue;
}else{
sum = sum + x;
}
}
cout<<sum<<endl;
}else if(x < y){
x = x + 1;
for(;x<y;x++){
if(x%2 == 0){
continue;
}else{
sum = sum + x;
}
}
cout<<sum<<endl;
}else{
cout<<0<<endl;
}
return 0;
}