#include<stdio.h>
char a[25],b[25],c[25];
int i,n,t;
int main() {
    freopen("nunta.in","r",stdin),freopen("nunta.out","w",stdout),scanf("%d",&n),b[1]=2,c[1]=b[0]=c[0]=1;
    if(n>3) {
        for(;n>2;n--) {
            for(t=0,i=1;i<=b[0]||i<=c[0]||t;i++,t/=10)
                a[i]=(t+=b[i]+c[i])%10;
            for(a[0]=i-1,i=0;i<=b[0];i++)
                c[i]=b[i];
            for(i=0;i<=a[0];i++)
                b[i]=a[i];
        }
        for(i=a[0];i;i--)
            printf("%d",a[i]);
    }
    else
        printf("%d",n);
}