#include <fstream>

using namespace std;

ifstream f("fact.in");
ofstream g("fact.out");

long long p,n=0,c,nr=0,i,N;

int main()
{
    f>>p;
    do{
        n++;
        c=n;
        while(c!=0){
            N=c%5;
            if(N==0)
            nr++;
            else break;
            c=c/5;}
    }while(nr!=p);
    g<<n<<endl;
    return 0;
}