Bank operations

#include<stdio.h>
#include<stdlib.h>
int n;
struct bank_accnt
{
    int accnt_no,pwd,locked_status;
    float balance;
}acc[50];
struct bank_accnt deposit(struct bank_accnt a,float amount)
{
    a.balance+=amount;
    printf("%f was deposited to account number %d\n",amount,a.accnt_no);
    return a;
}
struct bank_accnt withdraw(struct bank_accnt a,float amount)
{
    if(a.balance==0)
    {
        printf("Nil balance in account number %d\nNo amount was withdrawn.",a.accnt_no);
        return a;
    }
    a.balance-=amount;
    printf("%f was withdrawn from account number %d\n",amount,a.accnt_no);
    return a;
}
void balance(struct bank_accnt a)
{
    printf("Balance in account number %d is %f\n",a.accnt_no,a.balance);
}
int acc_check(int ac_num)
{
    int i,flag=1;
    for(i=0;i<n;i++)
    {
        if(acc[i].accnt_no==ac_num)
        {
            flag=0;
            break;
        }
    }
    if(flag)
    {
        printf("Error! Account number %d does not exist!",ac_num);
        return -1;
    }
    else
        return i;
}
void main()
{
    int i,ch=-1,ac_num,password,err_flag,flag;
    float amount;
    printf("Enter the number of bank accounts needed:");
    scanf("%d",&n);
    for(i=0;i<n;i++)
    {
        err_flag=0;
        printf("Enter account number for account %d:",i+1);
        scanf("%d",&acc[i].accnt_no);
        acc[i].pwd=1;
        while(acc[i].pwd<1000 || acc[i].pwd>9999)
        {
            if(err_flag)
                printf("Invalid input! Enter a valid 4-digit number:");
            else
                printf("Enter 4-digit password:");
            scanf("%d",&acc[i].pwd);
            err_flag+=1;
        }
        printf("Enter starting balance for account %d:",i+1);
        scanf("%f",&acc[i].balance);
        acc[i].locked_status=0;
    }
    while(ch!=4)
    {
        printf("\n1.Deposit\n2.Withdrawal\n3.Balance Enquiry\n4.Exit\nEnter your choice:");
        scanf("%d",&ch);
        switch(ch)
        {
            case 1:
                printf("Enter the account number:");
                scanf("%d",&ac_num);
                flag=acc_check(ac_num);
                if(flag==-1)
                    break;
                if(acc[flag].locked_status)
                {
                    printf("Your account has been locked. Contact nearest branch for help.");
                    break;
                }
                printf("Enter the amount to be deposited:");
                scanf("%f",&amount);
                acc[flag]=deposit(acc[flag],amount);
                break;
            case 2:
                printf("Enter the account number:");
                scanf("%d",&ac_num);
                flag=acc_check(ac_num);
                if(flag==-1)
                    break;
                if(acc[flag].locked_status)
                {
                    printf("Your account has been locked. Contact nearest branch for help.");
                    break;
                }
                password=1;
                err_flag=0;
                while(password!=acc[flag].pwd)
                {
                    if(3==err_flag)
                    {
                        acc[flag].locked_status=1;
                        printf("Account locked! Contact the nearest branch for further help.");
                        goto jump;
                    }
                    if(err_flag)
                        printf("Incorrect password. %d tries left.\n",3-err_flag);
                    printf("Enter the 4-digit password:");
                    scanf("%d",&password);
                    err_flag+=1;
                }
                printf("Enter the amount to be withdrawn:");
                scanf("%f",&amount);
                acc[flag]=withdraw(acc[flag],amount);
                jump:
                break;
            case 3:
                printf("Enter the account number:");
                scanf("%d",&ac_num);
                flag=acc_check(ac_num);
                if(flag==-1)
                {
                    printf("check");
                    break;
                }
                if(acc[flag].locked_status)
                {
                    printf("Your account has been locked. Contact nearest branch for help.");
                    break;
                }
                password=1;
                err_flag=0;
                while(password!=acc[flag].pwd)
                {
                    if(3==err_flag)
                    {
                        acc[flag].locked_status=1;
                        printf("Account locked! Contact the nearest branch for further help.");
                        goto jump;
                    }
                    if(err_flag)
                        printf("Incorrect password. %d tries left.",3-err_flag);
                    printf("Enter the 4-digit password:");
                    scanf("%d",&password);
                    err_flag+=1;
                }
                balance(acc[flag]);
                break;
            case 4:
                exit(0);
                break;
            default:
                printf("Invalid input!");

        }
    }
}