#include <bits/stdc++.h>
using namespace std;
int p, step, pos;
int zero(int x)
{
    int p5 = 5, ans = 0;
    while(x/p5){
        ans += x/p5;
        p5*=5;
    }
    return ans;
}
int main() {
    freopen("fact.in", "r", stdin);
    freopen("fact.out", "w", stdout);

    scanf("%d", &p);
    step = 1 << 30;

    while(step > 0){
        if (zero(pos + step) < p){
            pos += step;
        }
        step /= 2;
    }

    if (zero(pos+1) == p){
        printf("%d\n", pos+1);
    }else{
        printf("%d\n", -1);
    }
    return 0;
}