poj 2591 Set Definition

#include<stdio.h>#define N 10000005int num[N];int main(){num[1]=1;int i,j,k,x1,x2;j=1,k=1;for(i=2;i<10000001;i++){x1=num[j]*2+1;x2=num[k]*3+1;if(x1>x2)x1=x2;num[i]=x1;if(num[j]*2+1==x1)j++;if(num[k]*3+1==x1)k++;}int n;while(scanf("%d",&n)!=EOF)printf("%dn",num[n]);return 0;}