C语言的问题，请帮个忙。我输入程序#include<stdio.h>

main()
{int a,b,sum;
printf("please input first number:\n");
scanf("%d",&a);
printf("please input second number:\n");
scanf("%d",&b);
sum=a+b;
printf("sum is %d\n",sum);
system("PAUSE");
}

#include<stdio.h>
main()
{int a,b,sum;
scanf("%d,%d",&a,&b);
sum=a+b;/*这里少了个分号*/
printf("sum is %d\n",sum);
}