#include <stdio.h>
#define MAX 1000000000

int cinci(long long p)
{
    int pow = 1, s = 0;
    while ( pow * 5 <= p)
    {
        pow *= 5;
        s += p/pow;

    }
    return s;
}

long long caut_bin(long long a, long long b, int p)
{
    long long mid;
    while( b - a > 1)
    {
        mid = (b + a) / 2 ;
        if (cinci(mid) < p)
            a = mid;
        else
            b = mid;
    }
    if(cinci (b) == p)
        return b;
    else
        return -1;
}


int main(void)
{
    long long p;
    freopen("fact.in", "r", stdin);
    freopen("fact.out", "w", stdout);
    scanf("%lld", &p);
    printf("%lld \n", caut_bin(0,MAX,p));
}