// #pragma GCC optimize("Ofast")
// #pragma GCC target("avx,avx2,fma")
// #pragma GCC optimization ("unroll-loops")

#include <bits/stdc++.h>

using namespace std;

void __print(int x) {cerr << x;}
void __print(long x) {cerr << x;}
void __print(long long x) {cerr << x;}
void __print(unsigned x) {cerr << x;}
void __print(unsigned long x) {cerr << x;}
void __print(unsigned long long x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}

template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? "," : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifndef ONLINE_JUDGE
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
#define debug(x...)
#endif
#define ll long long int

bool chck(int n,int mid){
    int i=5;
    int cnt=0;
    while(mid/i!=0){
        cnt+=mid/i;
        i=i*5;
    }
    return cnt>=n;
}

bool chck_ans(int n,int mid){
    int i=5;
    int cnt=0;
    while(mid/i!=0){
        cnt+=mid/i;
        i=i*5;
    }
    return cnt==n;
}

int main(){
    ifstream in("fact.in");
    ofstream out("fact.out");
    int n;
    in>>n;
    if(n==0){
        out<<"1\n";
        return 0;
    }
    int l=5;
    int r=n*5+1;
    int mid;
    int ans=-1;
    while(l<=r){
        mid=(l+r)/2;
        //debug(l,r,mid);
        if(chck(n,mid)){
            ans=mid;
            r=mid-1;
        }
        else{
            l=mid+1;
        }
        //break;
    }
    assert(ans!=-1);
    if(!chck_ans)ans=-1;
    out<<ans<<"\n";
    return 0;
}