#include <iostream>
#include <algorithm>
using namespace std;
int main()
{
long long int n1,n2,ans,flag;
while(cin>>n1)
{
cin>>n2;
flag=0;
if(n1==n2)
{
cout<<n1<<endl;
continue;
}
if(n1>n2)
{
swap(n1,n2);
}
if((n1<=0&&n2<=0))
{
flag=1;
n1=abs(n1);
n2=abs(n2);
ans = ((n2*n2-n1*n1)+(n2-n1))/2;
ans-=n2;
cout<<ans<<endl;
}
else if((n1>=0&&n2>=0))
{
flag=0;
n1=abs(n1);
n2=abs(n2);
ans = ((n2*n2-n1*n1)+(n2-n1))/2;
ans+=n1;
cout<<ans<<endl;
}
else
{
n1=abs(n1);
n2=abs(n2);
n1=(n1*(n1+1))/2;
n2=(n2*(n2+1))/2;
n1=-n1;
ans=n1+n2;
cout<<ans<<endl;
}
}
return 0;
}
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