#include <stdio.h>
#include <stdlib.h>
inline long long leg(int n){
    long long nr=0LL;
    long long p=5LL;
    while(p<=n){
        nr+=1LL*n/p;
        p*=5LL;
    }
    return nr;
}

int main()
{
    FILE*fin,*fout;
    int p;
    long long st,a;
    fin=fopen("fact.in","r");
    fout=fopen("fact.out","w");
    fscanf(fin,"%d",&p);
    fclose(fin);
    a=0LL;st=(1LL<<35);
    while(st>0LL){
        if (leg(st+a)<p)
            a+=st;
        st>>=1LL;
    }
    fprintf(fout,"%lld\n",a+1LL);
    fclose(fout);
    return 0;
}