#include<stdio.h>
long int div(long int a)
{
    long int nr=0;
    while(a%5==0)
    {
        nr++;
        a=a/5;
    }
    return nr;
}
int main()
{
    FILE *f=fopen("fact.in","r"),*g=fopen("fact.out","w");
    long int p,n=5,nr=0;
    int ok=0;
    fscanf(f,"%ld",&p);
    while(!ok)
    {
        nr+=div(n);
        if(nr==p) ok=1;
        if(n==p*5 && ok==0) {ok=1;n=-1;}
        n=n+5;
    }
    fprintf(g,"%ld",n-5);
    fclose(f);
    fclose(g);
    return 0;
}