1 #include<iostream>
  2 #include<cstdio>
  3 #include<cmath>
  4 #include<algorithm>
  5 #include<queue>
  6 #include<cstring>
  7 #define PAU putchar(' ')
  8 #define ENT putchar('\n')
  9 #define eps 1e-8
 10 using namespace std;
 11 const int maxn=105;
 12 struct bign{
 13     int len,s[maxn];
 14     bign(){memset(s,0,sizeof(s));len=1;}
 15     bign(int num){*this=num;}
 16     bign(const char *num){*this=num;}
 17     bign operator = (const int num){
 18         char s[maxn];  sprintf(s,"%d",num);
 19         *this = s;return *this;
 20     }
 21     bign operator = (const char *num){
 22         for(int i=0;num[i]=='0';num++);
 23         len=strlen(num);
 24         for(int i=0;i<len;i++) s[i]=num[len-i-1]-'0';
 25         return *this;
 26     }
 27     bign operator + (const bign &b) const{
 28         bign c;c.len=0;
 29         for(int i=0,g=0;g||i<max(len,b.len);i++)  {
 30             int x=g;
 31             if(i<len) x+=s[i];
 32             if(i<b.len) x+=b.s[i];
 33             c.s[c.len++]=x%10;
 34             g=x/10;
 35         } return c;
 36     }
 37     void clean(){while(len > 1 && !s[len-1]) len--;return;}
 38     bign operator * (const bign &b){
 39         bign c;
 40         c.len=len+b.len;
 41         for(int i=0;i<len;i++) for(int j=0;j<b.len;j++) c.s[i+j]+=s[i]*b.s[j];
 42         for(int i=0;i<c.len;i++){
 43             c.s[i+1]+=c.s[i]/10;
 44             c.s[i]%=10;
 45         } c.clean();return c;
 46     }
 47     bign operator - (const bign &b){
 48         bign c;c.len=0;
 49         for(int i=0,g=0;i<len;i++){
 50             int x=s[i]-g;if(i<b.len) x-=b.s[i];
 51             if(x>=0) g=0;
 52             else g=1,x+=10;
 53             c.s[c.len++]=x;
 54         } c.clean();return c;
 55     }
 56     bign operator / (const bign &b)  {
 57         bign c,f=0;
 58         for(int i=len-1;i>=0;i--){
 59             f=f*10;f.s[0]=s[i];
 60             while(!(f<b)) f=f-b,c.s[i]++;
 61         } c.len=len;c.clean();return c;
 62     }
 63     bign operator % (const bign &b)  {
 64         bign r = *this / b;
 65         r = *this - r*b;
 66         return r;
 67     }
 68     bool operator < (const bign &b)  {
 69         if(len!=b.len) return len<b.len;
 70         for(int i=len-1;i>=0;i--){
 71             if(s[i]!=b.s[i]) return s[i]<b.s[i];
 72         } return false;
 73     }
 74     bool operator > (const bign &b){
 75         if(len!=b.len) return len>b.len;
 76         for(int i=len-1;i>=0;i--){
 77             if(s[i]!=b.s[i]) return s[i]>b.s[i];
 78         } return false;
 79     }
 80     bool operator == (const bign &b){
 81         return !(*this>b)&&!(*this<b);
 82     }
 83     bool operator >= (const bign &b){
 84         return (*this>b)||(*this==b);
 85     }
 86     void print(){
 87         for(int i=len-1;i>=0;i--) putchar(s[i]+'0');return;
 88     }
 89 }f[maxn];
 90 inline int read(){
 91     int x=0,sig=1;char ch=getchar();
 92     while(!isdigit(ch)){if(ch=='-')sig=-1;ch=getchar();}
 93     while(isdigit(ch))x=10*x+ch-'0',ch=getchar();
 94     return x*=sig;
 95 }
 96 inline void write(int x){
 97     if(x==0){putchar('0');return;}if(x<0)putchar('-'),x=-x;
 98     int len=0,buf[15];while(x)buf[len++]=x%10,x/=10;
 99     for(int i=len-1;i>=0;i--)putchar(buf[i]+'0');return;
100 }
101 int n;
102 void init(){
103     n=read();f[1]=1;f[2]=5;
104     return;
105 }
106 void work(){
107     for(int i=3;i<=n;i++) f[i]=f[i-1]*3-f[i-2]+2;
108     return;
109 }
110 void print(){
111     f[n].print();
112     return;
113 }
114 int main(){init();work();print();}