Почему не правильно считает среднее арифметическое(в главной програме)

//---------------------------------------------------------------------------
 
#pragma hdrstop
 
//---------------------------------------------------------------------------
 
#pragma argsused
#include<stdlib.h>
#include<iostream.h>
#include<stdio.h>
#include<conio.h>
#define a 10//kilkist chisel u faile
void stv_file(char*name)//func.stvorennya failu
{FILE*f;
int i,d;
if((f=fopen(name,"w"))==NULL)
{       /*perror("Pomilka zapicy");
        exit(4); */
}
for(i=0;i<a;i++)
{d=random(51)-20;
putw(d,f);
}
fclose(f);
}
void vuvid_file(char*name)//func.vuvodu vmistu failu
{FILE*f;
int d;
if((f=fopen(name,"r"))==NULL)
{       //perror("Pomilka vmistime failu dlya zchituvannya\n");
        //exit(3);
}
for(;(d=getw(f))!=EOF;)
cprintf("%d%s",d,"  ");
fclose(f);
getch();
}
void minn(char*name)//func/dlya poshuku minimalnogo elementa
{FILE*f;
int d,i,min;
if ((f=fopen(name,"r"))==NULL)
{       //perror("File not exist");
        //exit(3);
}
for(min=100;(d=getw(f))!=EOF;)
if (d<min) min=d;
cout<<"\nmin=\n"<<min;
fclose(f);
getch();
}
void maxx(char*name)//func.dlya poshuku maximalnogo elementa
{FILE*f;
int d,i,max;
if ((f=fopen(name,"r"))==NULL)
{       //perror("File not exist");
        //exit(3);
}
for(max=0;(d=getw(f))!=EOF;)
if (d>max) max=d;
cout<<"\nmax=\n"<<max;
fclose(f);
getch();
}
int main()
{randomize();int s,max,min;
char name[30];
clrscr();
cout<<"\nVv/imya failu\n";
gets(name);
stv_file(name);
cout<<"\nVmist f.\n";
vuvid_file(name);
minn(name);
maxx(name);
s=(max+min)/2;//srednee arifmeticheskoe
cout<<"\nS=\n"<<s;//srednee arifmeticheskoe(vuvod)
getch();
return 0;
}
//---------------------------------------------------------------------------