#include<stdio.h>
using namespace std;
FILE *f,*g;
int v[18]={0,5,25,125,625,3125,15625,78125,390625,1953125,9765625,48828125,244140725};
int main()
{
    long long p,s,d,mij,n=-1,nr0,i;
    f=fopen("fact.in","r");
    g=fopen("fact.out","w");
    fscanf(f,"%lld",&p);
    if(p!=0)
    {
        s=1;
    d=p*5;
    while(s<=d)
    {
        mij=(s+d)/2;
        nr0=0;
        for(i=1;v[i]<=mij;i++)
        {
            nr0=nr0+mij/v[i];
        }
        if(nr0==p)
        {
            n=mij;
            d=mij-1;
        }
        else
        {
            if(nr0>p)
            {
                d=mij-1;
            }
            else
            {
                s=mij+1;
            }
        }
    }
    fprintf(g,"%lld",n);
    }
    else
    {
        fprintf(g,"1");
    }

    fclose(f);
    fclose(g);
    return 0;
}