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

using namespace std;

int nr0(int n){
    int nr=0;
    int p=5;
    while(p<=n){
        nr+=n/p;
        p*=5;
    }
    return nr;
}

int main()
{
    FILE *fin, *fout;
    int n,p5,p,rez,pas,zero;
    fin=fopen("fact.in","r");
    fout=fopen("fact.out","w");
    fscanf(fin,"%d",&p);
    rez=0;
    for(pas=1<<28;pas;pas>>=1){
        if(nr0(rez+pas)<p)
            rez+=pas;
    }
    rez++;
    if(nr0(rez)!=p)
        fprintf(fout,"-1");
    else
        fprintf(fout,"%d",rez);
    fclose(fin);
    fclose(fout);
    return 0;
}