#include <stdio.h>
#include <stdlib.h>
int zero( int n){
    int nr=0;
    while(n>=5)
        nr+=(n/=5);
    return nr;
}
int main()
{
    int p2=1<<30,p,i;
    FILE*fin,*fout;
    fin=fopen("fact.in","r");
    fscanf(fin,"%d",&p);
    fclose(fin);
    i=0;
    while(p2>0){
      if(zero(i+p2)<p)
        i+=p2;
      p2/=2;
    }
    fout=fopen("fact.out","w");
    fprintf(fout,"%d",i+1);
    fclose(fout);
    return 0;
}