#include<stdio.h>


int main(){
long p,n,i,j,aux=0,ready=0;
freopen("fact.in","rt",stdin);
freopen("fact.out","w+",stdout);

scanf("%ld",&p);
if(p==0){
 printf("1");
 return 0;
}
if(p==1){
 printf("5");
 return 0;
}

for(i=1;!ready;i++){
 for(j=i;(j%5==0)&&(j>0);j++,j/=5)
  aux++;
 if(aux>=p)
  ready=1;
}

if(aux==p)
 printf("%ld",aux);
else printf("-1");

}