#include <iostream>
#include<fstream>
using namespace std;

ifstream fin("fact.in");
ofstream fout("fact.out");

int yeet(int x){
    int ynot=0,yes=5;
    while(yes<=x){
        ynot+=x/yes;
        yes*=5;
    }
    return ynot;
}

int main()
{
    int P,st=0,dr=2000000000,no_u=-1,check_mid;
    fin>>P;
    while(st<=dr){
        check_mid=(st+dr)/2;
        if(yeet(check_mid)==P)
            no_u=check_mid;
        if(yeet(check_mid)>=P)
            dr=check_mid-1;
        else
            st=check_mid+1;
    }
    if(no_u==0)
        fout<<1;
    else
        fout<<no_u;
    return 0;
}