#include <cstdio>

int N;
unsigned char f1[210]={1,1},f2[210]={1,2};
unsigned char *F1=f1,*F2=f2,*AX;
void add(unsigned char A[], unsigned char B[])
{
    // Se calculeaza stiind ca B>=A
    int t=0;
    A[0]=B[0];
    for(int i=1; i<=B[0]; i++)
     {
         A[i]+=B[i]+t;
         t=A[i]/10;
         A[i]%=10;
    }
    if(t>0) A[++A[0]]=t;
}
int main()
{
    FILE *f;
    f=fopen("nunta.in","r");
    fscanf(f,"%d",&N);
    fclose(f);
    for(int i=1; i<=N; i++)
    {
        add(F1,F2);
        AX=F1;
        F1=F2;
        F2=AX;
    }
    f=fopen("nunta.out","w");
    if(N<=2) fprintf(f,"%d", N);
    else
    for(int i=f2[0]; i>0; i--)
       fputc(char(f2[i]+'0'),f);
       //fprintf(f,"%c",char(f1[i]+'0'));
    fclose(f);
    return 0;
}