unable to read a string inside a loop structure using fgets() function

Question

I used fgets() and gets() also for getting a string as input inside a loop. In the first execution, it worked properly but in the second time, it skips the inputting step and straight away goes to the next line.

#include<stdio.h>
#include<conio.h>
struct student
{
    int roll,m[3];
    float avg;
    char name[30];
}s[5];
void main()
{
    int i;
    clrscr();
    printf("Enter thr student details:");
    for(i=0;i<5;i++)
    {
        printf("\nstudent[%d] name:",i+1);
        fgets(s[i].name,30,stdin);
        printf("student[%d] register number:  ",i+1);
        scanf("%d",&s[i].roll);
        printf("student[%d] marks:\n",i+1);
        scanf("%d%d%d",&s[i].m[0],&s[i].m[1],&s[i].m[2]);
        s[i].avg=(s[i].m[0]+s[i].m[1]+s[i].m[2])/3;
    }
    printf("-----------------------------------------------------------");
    printf("\n  NAME        REG.NO      AVERAGE");
    printf("\n-----------------------------------------------------------");
    printf("\n      DISTINCTION");
    for(i=0;i<5;i++)
        if(s[i].avg>74)
            printf("\n%-20s%-10d%.2f",s[i].name,s[i].roll,s[i].avg);
    printf("\n              FIRST CLASS");
    for(i=0;i<5;i++)
        if((s[i].avg<74)&&s[i].avg>50)
            printf("\n%-20s%-10d%.2f",s[i].name,s[i].roll,s[i].avg);
    printf("\n                 FAIL");
    for(i=0;i<5;i++)
        if(s[i].avg<50)
            printf("\n%-20s%-10d%.2f",s[i].name,s[i].roll,s[i].avg);
    getch();
}

Answer 1

as told by @chux , scanf leaves '\n' in the stdin ( memory buffer ) , and fgets() takes value until there is a '\n' in the buffer , in order to clear the buffer the statement fflush(stdin); is used before the fgets() statement