#include <fstream>
using namespace std;

int zero_fact(int n){
    int p=5,nrzr=0;
    while(n>=p){
        nrzr+=n/p;
        p*=5;
    }
    return nrzr;
}

int caut(int st, int dr, int x )
{
    int mid,save=-1;
    while ( st<=dr )
    {
        mid=( st+dr )/2;
        int U=zero_fact(mid);
        if( x>U ) st=mid+1; else dr=mid-1;
         if( U == x ) save=mid;
    }
    return save;
}

int main()
{
    ifstream in("fact.in");
    ofstream out("fact.out");
    int p; in>>p;
    out<<caut(1,1<<30,p );
    return 0;
}