#include <fstream>
using namespace std;

int n;
long long p;

long long countZeros(long long x){
    long long res=0;

    long long pw5=5;
    while(pw5<=x){
        res+=x/pw5;
        pw5*=5;
    }

    return res;
}

int main(){
    ifstream cin("fact.in");
    ofstream cout("fact.out");

    cin>>p;

    long long sol;
    long long step=(1<<30);
    for(sol=0;step>0;step>>=1)
        if(countZeros(sol+step)<p)
            sol+=step;

    cout<<sol+1;

    return 0;
}