#include<stdio.h>
he(int n,int m)
{
int sum=0;
if(n==m)
return(n);
else
return(n+he(n+1,m));
}
main()
{
int n,m;
scanf("%d%d",&n,&m);
printf("%d",he(n,m));
}
#include<stdio.h>
he(int n,int m)
{
int sum=0;
if(n==m)
return(n);
else
return(n+he(n+1,m));
}
main()
{
int n,m;
scanf("%d%d",&n,&m);
printf("%d",he(n,m));
}