#include <bits/stdc++.h>
#define nmax 1e8
using namespace std;
ifstream fin ("fact.in");
ofstream fout ("fact.out");
vector <int> v;

int nr0(int qq){
    int sum=0;
    for(int i=0;i<v.size();++i)
        sum+=qq/v[i];
    return sum;
}

void make(){
    long long int x=5;
    while(x<=nmax*10){
        v.push_back(x);
        x*=5;
    }
}

int main()
{
    int n,p=1,q=5*nmax,maxo=-1;
    make();
    fin>>n;
    while(p<=q){
        int m=(p+q)/2;
        if(nr0(m)==n){maxo=m;q=m-1;}
        else if(nr0(m)>n) q=m-1;
        else p=m+1;
    }
    fout<<maxo<<'\n';
    return 0;
}