#include <iostream>
#include <fstream>

using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");

int main(){
    int p,nr0,nr5,ci,i;

    in>>p;
    if(p==0)
    out<<"1";
    else
    for(i=5;nr0<p;i=i+5){
    ci=i;
    while(ci>1){
    ci=ci/5;
    nr0++;
    }
    }
    if(p!=0)
    out<<i-5;

    return 0;
}