#include <cstdio>

inline int nfive(int a){
	int nf=0;
	while(a%5==0){
		a/=5;
		nf++;
	}
	return nf;
}
int main(){
	int P,N=0;

	FILE *fin,*fout;

	fin=fopen("fact.in","r");
	fout=fopen("fact.out","w+");

	fscanf(fin,"%u",&P);
	fclose(fin);

	if(P==0){
		N=-1;
	}else{
		int tf=1,n,i=5;
		while(tf<P){
			tf+=nfive(i);
			i+=5;
		}
		if(tf==P){
			N=i;
		}else if(tf>P){
			N=-1;
		}
	}

	fprintf(fout,"%d",N);

	fclose(fout);
}