#include <stdio.h>

int main()
{
    FILE *fin, *fout;
    int n, p, power5, nr_zero, dif, n2;
    fin=fopen("fact.in", "r");
    fscanf(fin, "%d", &p);
    fclose(fin);
    if(p==0){
      n=1;
    }
    else{
      n=p*5;
      nr_zero=0;
      power5=5;
      while(power5<n){
        nr_zero+=n/power5;
        power5*=5;
      }
      dif=nr_zero-p;
      n2=n;
      while(dif!=0){
        if(dif>0){
          n2-=dif*5;

        }
      }
    }
    fout=fopen("fact.out", "w");
    fprintf(fout, "%d", n2);
    fclose(fout);
    return 0;
}