#include <stdio.h>
#include <stdlib.h>
#define MAXN 500000000
inline int zeros(int x){
int con=0;
long long p5=5;
while(p5<x){
con+=x/p5;
p5*=5;
}
return con;
}
int main(){
FILE*fi,*fout;
int st,dr,mij,x,n,poz;
fi=fopen("fact.in" ,"r");
fout=fopen("fact.out" ,"w");
fscanf(fi,"%d" ,&n);
if(n==0)
fprintf(fout,"1");
else{
st=-1;
dr=MAXN;
while(st<=dr){
mij=(st+dr)/2;
x=zeros(mij);
if(x<=n){
st=mij+1;
poz=mij;
}
else
dr=mij-1;
}
while(poz%5>0)
poz--;
if(zeros(poz)==n)
fprintf(fout,"%d" ,poz);
else
fprintf(fout,"-1");
}
fclose(fi);
fclose(fout);
}