#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int main()
{
    int p;
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    scanf("%d",&p);
    int i,k=0;
    if(p==0)
    {
        printf("1");
        return 0;
    }
    for(i=1; i<=p; i++)
    {
        int c=0;
        int d=i*5;
        while(d%25==0)
        {
            c=c+2;
            d=d/25;
        }
        if(d%5==0)
            c++;
        k=k+c;
        if(k==p)
        {
            printf("%d",i*5);
            break;
        }
        if(k>p)
        {
            printf("-1");
            break;
        }
    }

    return 0;
}