关于四则运算的程序练习

#include<stdlib.h>
#include<stdio.h>
#include<time.h>
#include"math.h"
#include<conio.h>

void main()
{
int a,b,c,d,e,r,i,v,an;
char ch1[4]={'+','-','*','/'};
char ch2[4]={'+','-','*','/'};
for(i=0;i<10;i++)
{
a=rand()%100;
b=rand()%100;
c=rand()%100;
d=rand()%4;
e=rand()%4;
printf("%d %c %d %c %d",a,ch1[d],b,ch2[e],c);
printf("=");
if((ch1[d]=='+'||'-')&&(ch2[e]=='*'||'/'))
{
if(e==2)
{
v=c*b;
}
if(e==3)
{
v=b/c;
}
if(d==0)
{
r=a+v;
}
if(d==1)
{
r=a-v;
}
}
else
{
if(d==0)
{
v=a+b;
}
if(d==1)
{
v=a-b;
}
if(d==2)
{
v=a*b;
}
if(d==3)
{
v=a/b;
}
if(e==0)
{
r=v+c;
}
if(e==1)
{
r=v-c;
}
if(e==2)
{
r=v*c;
}
if(e==3)
{
r=v/c;
}
}
loop:scanf("%d",&an);
if(an==r)
{
printf("OK!");

}
else
{
printf("it does not matter and try it again:");
goto loop;
}
}

}