哪位大佬帮忙看一下错了哪里？


#include <stido.h>

int mian (viod)
{
int a,b;

double r;

printf("整数a和b的值:");
scanf("%d%d",&a,&b);

printf("a+b=%d\n",a+b);
printf("a-b=%d\n",a-b);
printf("a*b=%d\n",a*b);
printf("a/b=%d\n",a/b);
printf("a%%b=%d\n",a%b);
printf("(a+b)/2\n",(a+b)/2);
printf("平均值=%f\n\n",(double)(a+b)/2);

printf("半径:");
scanf("%1f",&r);
printf("半径为%.3f的圆的面积是%.3f。\n",r,3.14*3.14*r);

return 0;
}