#include<stdio.h>
int main(){
long int n,k,i,aux;

FILE *f=fopen("fact.in","r");
fscanf(f,"%ld",&n);
fclose(f);

k=0;i=5;

while(k<n){
aux=i;
  while(aux%5==0){
  k++;
    if(k>=n)break;
  aux=aux/5;
  }
i=i+5;
}
FILE *g=fopen("fact.out","w");
fprintf(g,"%ld",i-5);
fclose(g);



return 0;
}