#include <cstdio>

using namespace std;

int zero(int x)
{
    int z=0;
    while(x>=1)
    {
        x/=5;
        z+=x;
    }

    return z;
}

int main()
{
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);

    int p;
    int mid;
    int st,dr;
    st=0;
    dr=(1<<31)-1;

    scanf("%d",&p);

    bool ok=true;

    while(st<=dr && ok)
    {
        mid=(st+dr)/2;
        if(zero(mid) == p)
            ok=false;
        else
            if(zero(mid)<p)
                st=mid+1;
            else
                dr=mid-1;
    }

    if(ok)
        printf("-1");
    else
    {
        while(mid%5)
            --mid;
        printf("%d",mid);
    }

    return 0;
}