#include<algorithm>
using namespace std;

int p;

inline int solve (int n)
{
    int i,sol=0;
    for(i=5;i<=n;i*=5)
        sol+=n/i;
    return sol;
}
int main ()
{
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    int st=1,dr=1<<30,mij,sol;
    scanf("%d",&p);
    while(st<=dr)
    {
        mij=(st+dr)/2;
        if(solve(mij)>=p)
            sol=mij,dr=mij-1;
        else
            st=mij+1;
    }
    if(solve(sol)==p)
        printf("%d",sol);
    else
        printf("-1");
    return 0;
}