#include <stdio.h>
using namespace std;
FILE *f,*g;
int v[18]={0,5,25,125,625,3125,15625,78125,390625,1953125,9765625,48828125,244140725,1220703125};
int main()
{
    long long p,i,n0,n=-1,mij,s,d;
    f=fopen("fact.in","r");
    g=fopen("fact.out","w");
    fscanf(f,"%lld",&p);
    if(p>=1)
    {
        s=1;
        d=p*5;
        while(s<=d)
        {
            mij=(s+d)/2;
            n0=0;
            for(i=1;v[i]<=mij;i++)
                n0+=mij/v[i];
            if(n0==p)
            {
                n=mij;
                d=mij-1;
            }
            else if(n0<p)
                s=mij+1;
            else
                d=mij-1;
        }
        fprintf(g,"%lld",n);
    }
    else
        fprintf(g,"1");
    return 0;
}