#include <iostream>
#include <stdio.h>
using namespace std;
FILE*f=fopen("fact.in","r");
FILE*g=fopen("fact.out","w");
int main()
{
    int p,n,i=5,ok=0,x,s;
    fscanf(f,"%d",&p);
    while (!ok){
        x=i/5; s=0;
        while (x){
            s+=x;
            x/=5;
        }
        if (s==p) {n=i; ok=1;}
        i+=5;
    }
    fprintf(g,"%d",n);
    fclose(f);
    fclose(g);
    return 0;
}