#include <fstream>

using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
long long v[30];
int main()
{
    int p;
    fin>>p;
    long long p5=1;
   
    while(v[0]<=25)
    {p5=p5*5;
     v[++v[0]]=p5;
    }
    /*for(int i=1;i<=v[0];i++)
     fout<<v[i]<<"\n";*/
    
    int x=0,af=0,i,j;

    if(p==0) fout<<1;
    else
    for(i=1;i<v[0];i++)
    {
        x=x+i;
        if(x>p) {fout<<-1;break;}
        else if(x==p) {fout<<v[i];break;}
        for(j=v[i]+5;j<v[i+1];j=j+5)
        {
            if(j%v[i]==0) x=x+i;
            else x++;
            if(x==p) {af=1;fout<<j;break;}
        }
        if(af==1) break;
    } 
    
    return 0;
}