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