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#include <fstream>
using namespace std;
ifstream fin ("fact.in");
ofstream fout ("fact.out");
int n;
int nrZero ( int x )
{
int s = 0, p = 5;
while ( p <= x )
{
s += x / p;
p *= 5;
}
return s;
}
int binSearch ( int n )
{
int t, pp = -1, mij, st = 1, dr = 100000000;
while ( st <= dr )
{
mij = (st + dr) / 2;
t = nrZero(mij);
if ( t >= n )
dr = mij - 1, pp = mij;
else
st = mij + 1;
}
return pp;
}
int main()
{
fin >> n;
if ( n == 0 )
fout << 1;
else
{
int t = binSearch (n);
if ( nrZero(t) == n )
fout << t;
else
fout << -1;
}
}