帮忙看看哪错了

#include<conio.h>
#include<stdio.h>
#include<string.h>
#define N 80
int fun(char *s,char *t)
{ int n;
  char *p,*r;
  n=0;
  while(*s)
  { p=s;
    r=p;
   while(*r)
    if(*r==*p) {r++;p++;}
    else break;
   if(*r==0)
    n++;
   s++;
  }
  return n;
}
main()
{ char a[N],b[N]; int m;
clrscr();
printf("\nPlease enter string a:"); gets(a);
printf("\nPlease enter substring b:"); gets(b);
m=fun(a,b);
printf("\nThe result is: m=%d\n",m);
}
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要实现什么功能啊  
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