[t005] sum

#include<stdio.h>
long sum(long i)
{
    if(i==1)
    {
        return i;
    }
    else
    {
        return i+sum(i-1);
    }
}
int main()
{
    long i;
    scanf("%ld",&i);
    printf("%ld",sum(i));
    return 0;
}