#include<stdio.h>

long p, i, nrcinci, j, x;
int ok;

int main ()
{
    freopen("fact.in", "r", stdin);
    freopen("fact.out", "w", stdout);
    scanf("%ld", &p);

    i=1;
    while ((i<=5*p)&&(ok==0))
        {
            nrcinci=0;
            for (j=1; j<=i; j++)
                {
                    x=j;
                    while (x%5==0)
                        {
                            x=x/5; nrcinci=nrcinci+1;
                        }
                }
            if (nrcinci==p) {printf("%ld", i); ok=1;}
            i=i+1;
        }
    if (p==0) printf("%d", 1);
    return 0;
}