#include <stdio.h>

int nr_zerouri(int x){
    int ras = 0, t = 5;
    while(x >= t){
        ras += (x/t);
        t *= 5;
    }
    return ras;
}

int main(){
    freopen("fact.in", "r", stdin);
    freopen("fact.out", "w", stdout);
    int p;
    scanf("%d", &p);
    int st = 1, dr = p*5;
    while(st <= dr){
        int mij = (st+dr)/2;
        if(nr_zerouri(mij) < p)
            st = mij + 1;
        else
            dr = mij - 1;
    }
    if(nr_zerouri(st) == p)
        printf("%d", st);
    else
        printf("%d", -1);
    return 0;
}