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