#include <fstream>

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

int nz(int x){
    int ans=0;
    int p5=5;
    while(x>=p5){
        ans=ans+x/p5;
        p5=p5*5;
    }
    return ans;
}

int main()
{   int p;
    in>> p;
    int st=1;
    int dr=5*p;

    while(st<=dr){
        int mij=(st+dr)/2;
        if(nz(mij)<p){
            st=mij+1;
        } else{
            dr=mij-1;
        }
    }
    if(nz(st)==p){
        out<< st;
    } else{
        out<< "-1";
    }

    return 0;
}