#include <stdio.h>

int main(){
  int n,i;
  FILE *f = fopen("nunta.in","r");
  fscanf(f,"%d",&n);
  fclose(f);
  FILE *g = fopen("nunta.out","w");
  if (n<2) {
    fprintf(g,"%d",1);
  } else {
    long int f1=1,f2=1,f3;
    for (i=1;i<=n-1;i++) {
      f3 = f1+f2;
      f1=f2;
      f2=f3;

    }
    fprintf(g,"%ld",f3);
  }

  fclose(g);
  return 0;
}