#include <stdio.h>
int p,put[12]={5,25,625,3125,15625,78125,390625,1953125,9765625,48828125,244140625,1220703125};
int s,e,mij,val;
int main()
{
    FILE *fin,*fout;
    fin=fopen("fact.in","r");
    fout=fopen("fact.out","w");
    unsigned long long nr;
    fscanf(fin,"%d",&p);
    s=1;
    e=900000000;
    int counter,val=-1;
    while(s<=e)
    {
        mij=(s+e)/2;
        counter=0;
        for(int i=0;;i++)
        {
            if(put[i]>mij) break;
            counter+=(mij/put[i]);
        }
        if(counter==p)
        {
            val=mij;
            break;
        }
        else
        {
            if(counter<p) s=mij+1;
            else if(counter>p) e=mij-1;
        }
    }
    val-=(val%5);
    fprintf(fout,"%d ",val);
}