#include<fstream.h>
ifstream f("fact.in");
ofstream g("fact.out");
long li,ls,i,p,d,m;
long nrz(long x)
{
long nr,oo;
oo=5;
nr=0;
while(oo<=x)
{
nr=nr+x/oo;
oo=oo*5;
}
return nr;
}
int main()
{
f>>p;
d=-1;
li=1;
ls=2000000000;

while(li<=ls)
{
m=li+ls;
m=m/2;
if(nrz(m)==p)
{if(m==d)
break;
else
{d=m;
ls=m;
}   }
else
if(nrz(m)<p)
li=m+1;
else
ls=m-1;
}
if(d==-1)
g<<"-1";
else
g<<d;
f.close();
g.close();
return 0;
}