#include <bits/stdc++.h>
using namespace std;

ifstream fin("fact.in");
ofstream fout("fact.out");

int main(){

    int P,N=0,i,fact,c;
    fin >> P;
    bool gasit = false;
    while(!gasit){
        N++;
        c=0;
        for(i=1;i<=N;i++)
        {
            if(i%2==0 && i%5==0)
            {
                while(i%2==0 && i%5==0){
                    c++;
                    if(i%2==0)
                        i/=2;
                    else
                        if(i%5==0)
                            i/=5;
                }
            }
        }
        if(c==P)
            gasit = true;
        else
            if(c>P)
                gasit = true;
    }
    if(c==P)
        fout << N;
    else
        fout << "-1";
    return 0;
}