Problem when using fgets for input of string [duplicate]

I had to write an assignment in C, where we had to define a structure and perform some operations on it. This is the code I have written:

#include <stdio.h>

struct student {
    char name[100];
    int roll_no;
    int chem, phy, math, total;
};

int main() {
    int n;
    printf("Enter the number of students: ");
    scanf("%d", &n);

    struct student s[n];
    for(int i = 0; i < n; i++) {
        printf("Enter the name of the student: ");
        gets(s[i].name);
        printf("Enter the roll number of the student: ");
        scanf("%d", &s[i].roll_no);
        printf("Enter the marks of phy, chem and maths: ");
        scanf("%d %d %d", &s[i].phy, &s[i].chem, &s[i].math);
        s[i].total = s[i].phy + s[i].chem + s[i].math;
    }

    printf("\n\nMerit List\n");
    printf("Rank \tName \tRollno \tPhy \tChem \tMaths \tTotal\n");
    for(int i = 0; i < n; i++) {
        printf("%d \t%s \t%d \t%d \t%d \t%d \t%d\n", i + 1, s[i].name, s[i].roll_no, s[i].phy, s[i].chem, s[i].math, s[i].total);
    }

    return 0;
}

When I compile and run this function, I am not able to input the values properly. I am not even seeing the input message properly, as this is the input message.

Enter the number of students: 2
Enter the name of the student: Enter the roll number of the student: skdjk 3
Enter the marks of phy, chem and maths: Enter the name of the student: Enter the roll number of the student: 3 4 6 dskj 2 
Enter the marks of phy, chem and maths: 

which was not what I expected. The output is also weird as I'm getting this:

Merit List
Rank    Name    Rollno  Phy     Chem    Maths   Total
1       32764   32700   1416183288  32768   1416248756
2   skdjk 3 1 3     3   4   6   -1028599268     -1028599258

When I took the string input using scanf, the issue is being resolved. Why does gets(and even fgets) cause these problems? How to resolve them?