#include <stdio.h>
#include <math.h>
#include <iostream>

using namespace std;
int intlog(double base, double x) {
    return (int)(log(x) / log(base));
}
int k,j,i,stop;
unsigned long S,n;

FILE*f=fopen("fact.in","r");
FILE*g=fopen("fact.out","w");
int main()
{
    fscanf(f,"%lu",&n);
    i=n*4;
    stop=1;
    while(stop)
        {
        S=0;
        k=intlog(5,i);
        for(j=1;j<=k;j++)
            S=S+i/pow(5,j);
        if(S==n) {fprintf(g,"%lu",i); return 0; }
        if(S>n) {fprintf(g,"-1");return 0;}
        i++;
        }
    fclose(f);
    fclose(g);
    return 0;
}