#include <cstdio>
using namespace std;

int ncz(int n)
{
    int s=0,p5=5;
    while(p5<=n)
    {
        s+=n/p5;
        p5*=5;
    }
    return s;
}

int main()
{
    int m,nc,st=0,dr=1000000000,p;
    FILE *f=fopen("fact.in","r");
    fscanf(f,"%d",&p);
    while(st<=dr)
    {
        m=(st+dr)/2;
        nc=ncz(m);
        if(p<=nc)dr=m-1;
        else st=m+1;
    }
    f=fopen("fact.out","w");
    if(p==0)fprintf(f,"1");
    else
    if(ncz(st)==p)
            fprintf(f,"%d",st);
    else
        fprintf(f,"%d",-1);
    return 0;
}