#include <stdio.h>

int main(){
    FILE *fin, *fout;
    fin=fopen("fact.in", "r");
    fout=fopen("fact.out", "w");

    int n, p, prod, gasit, j, i, pp;

    fscanf(fin, "%d", &p);

    if(p==0)
        j=1;
    else{
        i=1;
        gasit=0;
        while(gasit==0){
            j++;
            i=1;
            while(i<j){
                prod=prod*i;
                i++;
            }
           pp=0;
           while(prod%10==0){
                pp++;
                prod=prod/10;
           }
           if(pp=p)
                gasit=1;
        }
    }

    fprintf(fout, "%d", j);
    fclose(fin);
    fclose(fout);
    return 0;
}