#include <stdio.h>
#include <math.h>
int main(){
    int p, N;
    FILE * f1;
    FILE * f2;
    f1 = fopen ("fact.in","r");
    f2 = fopen ("fact.out","w");
    fscanf (f1, "%d", &p);
    //scanf("%d",&p);
    if(p) { N = 0; }
    else { N = 1; }
    while(p){
        N += 5;
        int aux = N;
        while(aux % 5 == 0 && aux){
            aux /= 5;
            if(p == 0){
                fprintf(f2,"-1\n");
                fflush(stdout);
                fclose(f1);
                fclose(f2);
                return 0;
            }
            p--;
        }
        //printf("N:%d\np:%d\n", N, p);
        //scanf("%d", &da);
    }
    //printf("N final:%d\n", N);
    fprintf(f2,"%d\n", N);
    fflush(stdout);
    fclose(f1);
    fclose(f2);
    return 0;
}