Winning CB Scholarship problem

#1

what is error in my code-------------
import java.util.;
public class Main {
public static boolean isValid(int mid,int M,int N,int X,int Y){
return midX <=M+(N-mid)*Y;
}
public static void main(String args[]) {
Scanner cin = new Scanner(System.in);
int N = cin.nextInt(), M = cin.nextInt(), X = cin.nextInt(), Y = cin.nextInt();
int low = 0, high = N;
int mid = (low+high)/2,temp = 0;
while(low<=high){
if(isValid(mid,M,N,X,Y)){
low = mid+1;
}else{
high = mid - 1;
}
temp = mid;
mid = (low+high)/2;
}
System.out.print(temp);
}
}

#2

store all the inputs in long due to the constraints given in the ques

import java.util.*;
public class Main {
//it should be mid*X-condition
public static boolean isValid(long mid,long M,long N,long X,long Y){
	if((mid*X<=Y*(N-mid)+M))
		return true;
    
	return false;
}
public static void main(String args[]) {
	Scanner cin = new Scanner(System.in);
	long N = cin.nextInt(), M = cin.nextInt(), X = cin.nextInt(), Y = cin.nextInt();
	long low = 0, high = N;
	long temp = 0;

	while(low<=high){
		long mid = (low+high)/2;
		if(isValid(mid,M,N,X,Y)){
			low = mid+1;
			temp=mid;
		}else{
			high = mid - 1;
		}
	}

	System.out.print(temp);
	}
}
#3

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