#include <stdio.h>

int main()
{
    FILE *fin, *fout;
    fin=fopen("fact.in", "r");
    fout=fopen("fact.out", "w");
    
    long p,a=0,b=0,n=1,x;
    
    fscanf(fin, "%ld", &p);
    
    while(a<p || b<p)
    {
       x=n;
       while(x%2==0)
       {
          a++;
          x/=2; }
       while(x%5==0)
       {
          b++;
          x/=5;}
       n++;
    }
    
    fprintf(fout, "%ld", n);
    fclose(fin); fclose(fout);
    
    return 0;
}