#include <fstream>

using namespace std;

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

int p,n=0,N,c,nr,i;
bool ok;

int main()
{
    f>>p;
    do{
        n++;
        N=1;
        for(i=1;i<=n;i++)
        N=N*i;
        nr=0;
        while(N!=0){
            ok=false;
            c=N%10;
            N=N/10;
            if(c==0)
            ok=true;
            if(ok==true)
            nr=nr+1;}
    }while(p!=nr);
    if(p==0)
    g<<1<<endl;
    else
    g<<n+3<<endl;
    return 0;
}