#include <stdio.h>
using namespace std;
int main()
{
    FILE *fin,*fout;
    fin=fopen("fact.in","r");
    fout=fopen("fact.out","w");
    long long int p;
    int count;
    fscanf(fin,"%lli",&p);
    long long int a[11]={5,25,125,625,3125,15625,78125,390625,1953125,9765625,48828125};
    if(p==0) fprintf(fout,"1");
    else
    {
        for(int i=5;;i+=5)
        {
            count=0;
            for(int j=0;j<11;j++)
            {
                if(a[j]<=i) count+=(i/a[j]);
                else break;
            }
            if(count==p)
            {
                fprintf(fout,"%lli",i);
                break;
            }
            else if(count>p)
            {
                fprintf(fout,"-1");
                break;
            }
        }
    }
}