How to calculate number of days?

CODE

How to calculate number of days?

Write a program to calculate number of days between given months

int main()

{

    int e,s,c,a[12],sum,i;

    printf("\n enter start month:");

    scanf("%d",&s);

    printf("\n enter end month:");

    scanf("%d",&e);

    c=s;

    for(i=0;i<=e-s;i++)

    {

        if(c==1||c==3||c==5||c==7||c==8||c==10||c==12)

            a[i]=31;

        else if(c==2)

            a[i]=28;

        else

            a[i]=30;

        c++;

    }

    if(c!=s)

    {

        sum=a[0];

        printf("\n %d",a[0]);

        for(i=1;i<=e-s;i++)

        {

            printf(" + %d",a[i]);

            sum+=a[i];

        }

        printf(" = %d",sum);

    }

    else

        printf("\n You have enter wrong information");

}

Output:

enter start month: 4

 enter end month:7

 30 + 31 + 30 + 31 = 122