#pragma option -3 -r -Z -O2 -a
#include<fstream.h>
int main()
{unsigned long gen,x;
long p,i;
ifstream f("fact.in");
f>>p;
f.close();
ofstream g("fact.out");
if(p==0){g<<"1"<<'\n';g.close();return 0;}
 else if((p<0)||(p>100000000)){g<<"-1"<<'\n';g.close();return 0;}
i=p;
gen=5;
while(i>0)
  {x=gen/5;
   i--;
   while((x%5)==0){i--;x=x/5;}
   gen+=5;
  }
if(i<0){g<<"-1"<<'\n';g.close();return 0;}
g<<gen-5<<'\n';
g.close();
return 0;
}