#include <bits/stdc++.h>
#define ll unsigned long long int
using namespace std;
ll p;
vector <ll> q;
static inline ll sum(ll val){
ll curr=0;
for(ll x:q)
    if(val/x==0)
        return curr;
    else curr+=val/x;
return curr;
}
static inline ll bin(){
ll st=1,dr=1e19,mid;
while(st<=dr){
    mid=(st+dr)/2;
    if(sum(mid)>=p)
        dr=mid-1;
    else st=mid+1;
}
return st;
}
int main()
{
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    scanf("%llu ",&p);
    ll curr=1;
    for(int i=1;i<=25;++i){
        curr*=5;
        q.push_back(curr);
    }
    printf("%llu ",bin());
}