#include <fstream>

using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");

int main()
{
    long long p, i = 0, cop, nr_zero = 0;
    fin >> p;
    if ( p == 0 )
    {
        fout << 1 << '\n';
        return 0;
    }
    while ( nr_zero < p )
    {
        i += 5;
        cop = i;
        while ( cop % 5 == 0 )
            ++nr_zero, cop /= 5;
    }
    fout << i << '\n';
    return 0;
}