#include <iostream> #include <cstring> using namespace std; int main() { int n1[50],n2[50],sum=0,i=0; while(cin>>n1[i]){ if(n1[i]==EOF){ break; } for(int j=1;j<=n1[i];j++){ n2[i]+=j; } } for(int j=1;j<=i-1;j++){ cout<<n2[j]; } return 0; }