//Ilie Dumitru
#include<cstdio>

int find(int P)
{
    int st=5, dr=P*5, mid, x, n;
    while(st<=dr)
    {
        mid=x=(st+dr)>>1;
        for(n=x/5, x/=5;x>4 && n<P;n+=x/5, x/=5);
        if(n==P)
        {
            while(mid%5)
                --mid;
            return mid;
        }
        if(n<P)
            st=mid+1;
        else
            dr=mid-1;
    }
    return -1;
}

int main()
{
    int P;
    freopen("fact.in", "r", stdin);
    freopen("fact.out", "w", stdout);
    scanf("%i", &P);
    fclose(stdin);
    if(P==0)
        printf("1");
    else
        printf("%i", find(P));
    fclose(stdout);
    return 0;
}