#include <stdio.h>
#include <math.h>
#define STUDENTS 5
#define EXAMS 3

typedef struct {
int id;
int math;
int english;
int physics;
double ave;
double std;
}Grades;

int main(void)
{
Grades data[]={{1,65,80,95},{2,70,68,75},{3,60,100,83},{4,100,55,74},{5,90,85,100}};
for(int i=0;i<STUDENTS;i++)
{
data[i].ave=(data[i].math+data[i].english+data[i].physics)/EXAMS;
data[i].std=sqrt(((data[i].math-data[i].ave)*(data[i].math-data[i].ave)+(data[i].english-data[i].ave)*(data[i].english-data[i].ave)+(data[i].physics-data[i].ave)*(data[i].physics-data[i].ave))/EXAMS);
printf("id %d :%.1f, %.1f\n",data[i].id,data[i].ave,data[i].std);
}
return 0;
}