/*
:s`                                                
                                               -:NMo/`                                              
                                           `.o/NsmMoNso:`                                           
                                        +y/N+MsmhhM+M+Msdy+h`                                       
                           `/:   .+:`   `dyddymsmsNoNoNoMoN/    -+/   ./-                           
                           .sos/`+yyd/ `--msMoN+Nomshhsmhds`- .yhyy`-ss++                           
                       //.`:smN+-+sos//o:`/hdhdymydhydymyh`.o+/ooh+::dNys``:+`                      
                      `syyy::y-/--..+/oyhs.dmmdysoooyhdmN+:hyy+/:.--:/+o-+dyy:                      
                   .:/.:do+:-`.+/oyhdmdyo+`.::/+osso++/:-`-oyydmhys+//`.:/od+--/-`                  
                 -soyh++/-+/oyhmdhhs/:--:/oossooo+/ooossso+/:--/oyhmmhhs+/+-+/shyo+                 
                 oh-+:..odmmhys+:::/+sssooo+/--.`   `.-:+ooossso+:::/oyhdmmy:`.o-+d.                
                 `--`   `/+://+ossooo+/:-.`               `-:/+ooossso//::o-    .-.                 
                           +h+so+/-.`    ```.-:./o-+--:.````   `.-:/ooo+d`                          
             .:+ooo/.`     +y/s       .---:/+::+o+-oo::+/::--.`      .d-m      `:+ooo/-`            
            /yhyyyyhho`    :d-y     .+hy/shhy/hhhy/hhhs/hhh+ohs:`    .y/d     /yhhyyyyho`           
           .hooyyyyo+/:-.` .m`d    :os+:ssss-ossso-ssss:osss//ss+`   /oss  `--/++syyysoy+           
           `oshhhhhy/-`     d:h`  ohhy-hhhhy:hhhhy:hhhhs/hhhh++hhy.  y-d:    `.:ohhhhhyo/           
            +hhhy+hy        sso/ .hdds+dddds+ddddy/ddddh:ddddh:hddo `d.m`       /hy+hhhy`           
           -hddds`+o.       -m-y -yyy//yyyy+/yyyyo-yyyyy-yyyyy-yyyo -y+y        ++-:ddddo           
           +dddddy/```````   d:h.`dmmd/mmmmh+mmmmd+mmmmd/mmmmy+mmm/ s:d:   .```` .odddddh`          
           :dddddddyyyhyos   +h/o .oss:+ssss.sssso-ssss//ssss-oss: .h:m   -yoyhyshddddddy           
           .ddddddddddy/:y   `m-h` `omNssNNNyyNNNm+NNNN/NNNd+dNh-  o/h+   :s:odddddddddd+           
           :ddddddddy/-ohs`   +y/o   `os//syy-syyo-yyy/+yso-ss:   .h:m    /yy::sdddddddds`          
         .smmmmmmmy. `hs..y.  `m:h.     ./::+yo+dm+Ns+ys/:/-      y:d/   o+`/d: `/dmmmmmmh:         
      `/ymmmmmmmdo`   `  oh.   :d-h              .``             /o+h    od. `    -hmmmmmmmdo-      
     -dmmmmmmmy/`       `y/     oy/y           -    `.`         -y:d.    `h:        -ommmmmmmms     
.::./smmmmmmmm/                 `ys/s`        /hs`+s++os:      :y:d-                 `dmmmmmmmd+--:-
-mmmm//hmNNNNh`                  `ys/s`      :y-oy+`   ``     /s:d-                   /mNNNNmo-ymmmo
+dNNNs``-hNNmo                     oy:s:    :h-  +y.   --   `o+/h.                    -hNNm/` /dNNNh
.osNNd/  yNmdo                      /h:+o` .s-    :oo+o+.  :s:ss`                     .mdmm- .yNNyh.
 .+mNN:`:Noody-                      .yo:s/``       ```  .o+/h/                      `+mh/my .yNNy-`
  -dhd-  -ss:-/o/.                    `/y//o:          .+o:ss.                    `:+o:-+y+`  hyNo` 
 .o/`h`    -hy.`/d-                     .oy//o-      .+o:oy:                      yh` +d+`    +/-o/ 
    `.      .ds  yy                       -ss:/o:` -++:+y/`                      :m- .N+       -  ` 
             /+  `.                         -ss::+o/:+y/`                        `.  -o`            
                                              -os/:os:`                                             
                                                ./o-                                                
                         .                                     `:-                                  
                        /m-             `-:::/++               `ds                                  
                       -syd`     .`    +h:`   `o`    ``       ``ho     `     ` `                    
                      `y..mo    /No/. -M/         `++:/s-  `//:/mo  `+/:s/  /d+s/                   
                      oo:-/N-   .M-   :M/         sm`  oN. hy   ho  yy::++  -M-`                    
                     +o    yd`  .M-    sd-`    :. sm`  +N. dh`  hs  hh` ``  -M.                     
                   `:y/`  `+y+- `ys/`   -++/::+o` `+o//o-  .sy+/hy- .syo+: `/y/` 
*/
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <queue>
#include <cmath>
#include <climits>
#include <iomanip>
#include <set>
#include <map>
using namespace std;
typedef long long ll;
int main(){
  ll bobu;
  cin >> bobu;
  ll babo = (1 + bobu) * bobu / 2;
  cout << babo << endl;//😷
}


Measured memory_bytes: 3572