#include <stdio.h>

 int main() {
   FILE *fin, *fout;
   int n, i, a, b, f;

   fin=fopen("kfib.in","r");
   fscanf(fin,"%d",&n);
   fclose(fin);

   a=0;
   if(n==1)
     b=a;
   else{
     b=1;
     for(i=2;i<n;i++){
       f=a+b;
       a=b;
       b=f;
     }
   }

   fout=fopen("kfib.out","w");
   fprintf(fout,"%d",b);
   fclose(fout);
   return 0;
 }