If user enters wrong password three times, then block the login for some minutes how to add below program

#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include <string.h>
main()


{
int i,counter=0,flag=0,log;
printf("Enter 1 to login")
switch(log)
{
    case 1:
char uid[25],pwd[25],s_uid[][25]={"user1","user2","user3"};
char s_pwd[][25]={"Pwd1","Pwd2","Pwd3"},ch='a';/*dummy character in ch */
printf("\n Enter the user id : ");
scanf("%s",uid);
printf("\n Enter the password : ");
i=0;
while(1)
{
    ch=getch();
    if(ch==13)
    break;
    else if(ch==8)
    {       if(i!=0) /*this is for avoiding the ENTER instructions getting deleted */
        {
            printf("\b");  /*printing backspace to move cursor 1 pos back*/
            printf("%c",32);/*making the char invisible which is already on console*/
            printf("\b"); /*printing backspace to move cursor 1 pos back*/
            i--;
            pwd[i]='\0';
        }
        else
        continue;
    }
    else
    {
    putchar('*');/* char - '*' will be printed instead of the character */
    pwd[i]=ch;
    i++;
    }
}
pwd[i]='\0';
for(i=0;i<=2;i++)
{
    if((stricmp(uid,s_uid[i]))==0 && (strcmp(pwd,s_pwd[i]))==0)
    {
        flag=1;
        break;
    }
}
if(flag) printf(" \n \n \t \t USER AUTHENTICATED ");
else printf("\n \n \n\t TRESSPASSERS WILL BE SHOT AND SURVIVORS WILL BE SHOT AGAIN :)");
}
getch();
}