hud 2709 Sumsets

#include <stdio.h>#include <math.h>__int64 xx[1000010];int main(){int i;xx[1]=1;xx[2]=2;for(i=3;i<=1000000;i++){if(i%2==0)xx[i]=(xx[i-2]+xx[i/2])%1000000000;elsexx[i]=xx[i-1];}while(~scanf("%d",&i))printf("%I64d\n",xx[i]);return 0;}