#include <iostream>
#include <fstream>
using namespace std;
long long int p,x,z,y;
int main()
{ifstream f("fact.in");
ofstream g("fact.out");
f>>p;
x=0;
z=0;
while(z<p){x=x+5;y=x;
   while(y%5==0) {z++;y=y/5;}}
if(p==0) g<<1;
else {if(p==z) g<<x;
else g<<-1;
}
}