#include<stdio.h>
int main()
{int p,k=0,i,P=1;
FILE *f=fopen("facto.txt","r");
FILE *g=fopen("facto.out","w");
fscanf(f,"%d",&p);
i=0;
while(k<p){i++;
           P=P*i;
	   if((i%5==0)||(i%10==0)) k++;}
fprintf(g,"%d",i);
fclose(f);
fclose(g);
return 0;
}