//#include<iostream>
#include<cstdio>

char a[210],b[210];
short nra,nrb;
FILE*f=fopen("nunta.in","r");
FILE*g=fopen("nunta.out","w");
inline void suma()
{

    int i;

    short aux,t=0,p;
    for(i=0;i<=nra||i<=nrb||t!=0;i++)
    {

        aux=a[i];
        a[i]=b[i];
        p=aux+t+b[i];
        b[i]=(aux+t+b[i])%10;
        t=p/10;

    }
    nra=nrb;
    nrb=i-1;

}
int main()
{
    short n;


    fscanf(f,"%d",&n);
    if(n<4)
        fprintf(g,"%d",n);
    else
    {

        a[0]=2;
        b[0]=3;
        nra=nrb=0;
        for(int i=4;i<=n;i++)
        {
            suma();
        }
        for(int i=nrb;i>=0;i--)
            fprintf(g,"%d",b[i]);
    }
    return 0;
}