#include<stdio.h>   
FILE *f,*g;   
int main()   
{   
f=fopen("fact.in","r");   
g=fopen("fact.out","w");   
long int p,s=0,i,j;   
int x[10000];   
fscanf(f,"%ld",&p);   
if(p==0) { i=1; fprintf(g,"%ld",i); }   
 else if(p<0) {i=-1; fprintf(g,"%ld",i); }   
 else {              
     while(p)
        {
           s=s+5;
           p--;
        }      
      }
 fprintf(f,"%ld",s)
 return 0;  
}