#include<iostream> using namespace std; int main(){ /** int n,sum=0; cin>>n; for(int a = 1;a<=n;a++){ sum=sum+a; } cout<<sum; **/ int n,m,sum = 0; cin>>n>>m; for(int a =n;a<=m;a++){ sum=sum+a; } cout<<sum; return 0; }