#include<stdio.h>
int main()
{
    int p,n,d,t,i;
    FILE *f1,*f2;
    f1=fopen("factorial.in","r");
    f2=fopen("factorial.out","w");
    fscanf(f1,"%d",&p);
    i=5;
    d=0;
    t=0;
    if(p==0){
             fprintf(f2,"%d",1);
             return 0;
             }
    while(t<=p)
    {
                    n=i;
                     while(n%5==0)
                     {d=d+1;
                     n=n/5;}
                     t=t+d;
                     i=i+5;
                     d=0;
    }
    fprintf(f2,"%d",i);
    fclose(f1);
    fclose(f2);
    return 0;
}