UVa 10079 Pizza Cutting Solution

#include<stdio.h>
int main()
{
int a,i,n;
long int b,c;
while(scanf("%d",&n)==1 && (n>=0))
{
a=0;
b=1;
for(i=0;i<=n;i++)
    {c=a+b;
    a=a+1;
    b=c;}
printf("%ld\n",c);
}
return 0;
}