#include <stdio.h>

int zero(int n){
    int nr=0;
    while (n>=5)
        nr+=(n/=5);
    return nr;
}

int main()
{
    FILE *fin,*fout;
    int p2,p,i;
    fin=fopen("fact.in","r");
    fout=fopen("fact.out","w");
    fscanf(fin,"%d", &p);
    for (i=0,p2=1<<30;p2>0;p2/=2)
        if (zero(i+p2)<p)
            i+=p2;
    fprintf(fout,"%d", i+1);
    return 0;
}