Electricity bill calculator in C

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#include<stdio.h>

#include<conio.h>

int main()

{

 printf("                           PUNJAB STATE POWER CORPORATION LIMITED \n");

 printf("                                                                                                          online portal\n");

 printf("choices: 1 for current month,  2 for prev months, 3 for other months\n\n");

 int choice, date, units;

 long long int password;

 double totalBill, extracharge, sum;

 char username[45];

 printf("                          username    ");

 gets(username);

 x:printf("                          password    ");

 scanf(" %lld",&password);

 if(password>9999)

 {

  printf("                         welcome      ");

  puts(username);

 }

 else

 {

  printf("                        wrong password\n");

  goto x;

 }

 a:printf("enter date- ");

 scanf("%d",&date);

 if(date>31)

 {

  printf("invalid input\n");

  goto a;

 }

 b:printf("                          enter your choice- ");

 scanf("%d", &choice);

 switch(choice)

 {

  case 1:

   {

    printf("enter units- ");

    scanf("%d",&units);

    if(units>0 && units<=100)

    {

     totalBill= units*0.50;

     printf("total bill= %lf\n",totalBill);

     extracharge= 0.0;

     printf("extracharge= 0.0\n");

     sum= extracharge+totalBill;

     printf("total sum to pay - %lf\n",sum);

    }

    else if(units>100 && units<=220)

    {

     totalBill= units*0.65;

     printf("total bill= %lf\n",totalBill);

     extracharge =0.0;

     printf("extracharge= 0.0\n");

     sum= extracharge+totalBill;

     printf("total sum to pay - %lf\n",sum);

    }

    else

    {

         totalBill= units*0.80;

         printf("total bill= %lf\n",totalBill);

         extracharge= 0.0;

         printf("extracharge = 0.0\n");

         sum= extracharge+totalBill;

         printf("total sum to pay= %lf\n",sum);

    }

    break;

   }

   

case 2:

 {

  printf("enter units- ");

    scanf("%d",& units);

    if(units>0 && units<=100)

    {

     totalBill=  units*0.98;

     printf("total bill= %lf\n",totalBill);

     extracharge=date*2.0;

     printf("extracharge= %lf\n",extracharge);

     sum= extracharge+totalBill;

     printf("total sum to pay - %lf\n",sum);

    }

    else if(units>100 && units<=220)

    {

     totalBill= units*1.65;

     printf("total bill= %lf\n",totalBill);

     extracharge= date*2.0;

     printf("extracharge= %lf\n",extracharge);

     sum=totalBill+extracharge;

     printf("total sum to pay= %lf\n",sum);

    }

    else

    {

         totalBill= units*2.36;

         printf("total bill= %lf\n",totalBill);

         extracharge= date*2.0;

         printf("extracharge= %lf\n",extracharge);

         sum= extracharge+totalBill;

         printf("total sum to pay= %lf\n",sum);

    }

    break; 

   }

 case 3:

   {

          printf("enter units- ");

    scanf("%d",& units);

    if(units>0 && units<=100)

    {

     totalBill=  units*0.98;

     printf("total bill= %lf\n",totalBill);

     extracharge=date*2.0+315.50;

     printf("extracharge= %lf\n",extracharge);

     sum= extracharge+totalBill;

     printf("total sum to pay - %lf\n",sum);

    }

    else if(units>100 && units<=220)

    {

     totalBill= units*1.65;

     printf("total bill= %lf\n",totalBill);

     extracharge= date*2.0+315.50;

     printf("extracharge= %lf\n",extracharge);

     sum=totalBill+extracharge;

     printf("total sum to pay= %lf\n",sum);

    }

    else

    {

         totalBill= units*2.36;

         printf("total bill= %lf\n",totalBill);

         extracharge= date*2.0+315.50;

         printf("extracharge= %lf\n",extracharge);

         sum= extracharge+totalBill;

         printf("total sum to pay= %lf\n",sum);

    }

    break; 

   }

 default:

  printf("                          invalid choice                               \n");

  goto b;

}

printf("                                  THANK YOU");

return 0;

getch();

}