萌新一个哪位大佬帮我看看哪里错了



#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;}