#include <fstream>

using namespace std;
ifstream cin("fact.in");
ofstream cout("fact.out");


int main()
{
int p;
int count5=0;
int i;
int copy_i;

cin>>p;

for(i=1; count5<p ;i++)
{
    copy_i=i;

    while(copy_i/5)
    {
        if(copy_i%5==0){
            count5++;
            copy_i=copy_i/5;
        }
        else break;

    }

}
cout<<i-1;
return 0;
}