POJ 2591

#include<iostream>
#include<stdio.h>
#define MAXN  10000001
using namespace std;

int a[MAXN];
void give_set();
int min(int i,int j);
int main()
{
    //freopen("acm.acm","r",stdin);
    give_set();
    int num;
    while(cin>>num)
    {
        cout<<a[num-1]<<endl;
    }
}

void give_set()
{
    a[0] = 1;
    int m;
    int len = 1;
    int x;
    int y;
    x = 0;
    y = 0;
    while(len < MAXN)
    {
        m = min(2*a[x]+1,3*a[y]+1);
        if(m == 2*a[x]+1) 
            ++ x;
        if(m == 3*a[y]+1)
            ++ y;
        a[len++] = m;
    }
}
int min(int a,int b)
{
    return a < b ? a : b;
}