#include <stdio.h>

int main(){
    long long s,p,nr,r,c;
    FILE *fin,*fout;

    fin=fopen("fact.in","r");
    fout=fopen("fact.out","w");
    fscanf(fin,"%lld",&p);

    c=0;
    nr=5;
    while(c<p){
      s=0;
      r=nr;
      while(r%5==0){
        s++;
        r/=5;
      }
      c+=s;
      nr+=5;
    }
    if(c==p){
      fprintf(fout,"%lld",nr-5);
    }else{
      fprintf(fout,"-1");
    }



    fclose(fin);
    fclose(fout);

    return 0;
}