#include <fstream>
std::ifstream cin("fact.in");
std::ofstream cout("fact.out");
int nz(int n)
{
    int k=5,aux,x=0;
    while(k<=n)
    {
        x+=n/k;
        k*=5;
    }
    return x;
}

int main()
{
    int i,p;
    std::cin>>p;
    for(i=1;;i++)
    {
        if(nz(i)==p)
        {
            std::cout<<i;
            return 0;
        }
    }
    return 0;
}