#include <fstream>

using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int v[101];
int C_bin(int x)
{
    int s=1,dr=v[0],mij;
    while(s<=dr)
    {
        mij=(s+dr)/2;
        if(x==v[mij]) return mij;
        else if(x<v[mij]) dr=mij-1;
        else s=mij+1;
    }
    return 0;
}
int main()
{
    int p;
    fin>>p;
    long long p5=1;
    while(v[0]<=50)
    {p5=p5*5;
     v[++v[0]]=p5;
    }
    
    if(p==0) fout<<1;
    else
    {
        int x=0,a=0,i;
        for(i=5;x<=p;i=i+5)
        { a=C_bin(i);
          if(a!=0) x=x+a;
          else x++;
          if(x>p) {fout<<-1;break;}
          else if(x==p) {fout<<i;break;}
        }
    }
    return 0;
}