#include <stdio.h>
#include <stdlib.h>

long factorial(int N){
    long fact = 1;

    while (N > 0){
        fact *= N;
        N--;
    }
    return fact;
}

int getRank(int P){
    int contor_zero = 0;
    int contor_doi = 0;
    int contor_cinci = 0;
    int N = 1;
    int aux = 0;

    do {
        aux = N;
        while (aux % 2 == 0){
            contor_doi++;
            aux /= 2;
        }
        aux = N;
        while (aux % 5 == 0){
            contor_cinci++;
            aux /= 5;
        }
        N++;
    }while ( (contor_doi < P) || (contor_cinci < P));


    return --N;
}


int main(void){

    FILE *in = freopen("factorial.in", "r", stdin);
    FILE *out = freopen("factorial.out", "w", stdout);
    int P;

    scanf("%d", &P);
    printf("%d", getRank(P));

    fclose(in);
    fclose(out);

    return 0;
}