#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
ll const mod=1000000007;
ll const md=998244353;
ll mypowr(ll a,ll b) {ll res=1;if(b<0)b=0;a%=mod; assert(b>=0);
for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
ll mypow(ll a,ll b) {ll res=1;if(b<0)b=0;assert(b>=0);
for(;b;b>>=1){if(b&1)res=res*a;a=a*a;}return res;}
ifstream in("fact.in");
ofstream out("fact.out");
#define mp make_pair
#define pb push_back
#define pf push_front
#define fi first
#define se second

#define cin in
#define cout out

ll solve(ll x){
ll cnt=0;
while(x>=5){
    cnt+=x/5;x/=5;
}
return cnt;

}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    cout<<fixed<<setprecision(15);

    ll n;
    cin>>n;
    if(n==0){cout<<"1\n";return 0;}
    ll lo=5;
    ll hi=500000005;
    while(lo<=hi){
        ll mid=lo+(hi-lo)/2;
        ll sum=solve(mid);
        if(sum==n&&mid%5==0){
            cout<<mid<<'\n';
            return 0;
        }
        if(sum>=n){
            hi=mid-1;
        }
        else{
            lo=mid+1;
        }
    }
    cout<<"-1\n";


    return 0;
}