// goodwincommaderek@gmail.com
import java.util.Scanner;

public class citybike {
    // assuming we want our number of bikes to always as high as possible
    static boolean canLowerBoundWork(int dlo, int N, int C, int[] arr) {
        int bikesHi = C;
        for (int n=0;n<N;n++) {
            bikesHi += arr[n] - dlo;
            bikesHi = Math.min(bikesHi, C);
            if (bikesHi < 0) {
                return false;
            }
        }
        return true;
    }
    // assuming we want our number of bikes to be as low as possible
    static boolean canUpperBoundWork(int dhi, int N, int C, int[] arr) {
        int bikesLo = 0;
        for (int n=0;n<N;n++) {
            bikesLo -= dhi - arr[n];
            bikesLo = Math.max(bikesLo, 0);
            if (bikesLo > C) {
                return false;
            }
        }
        return true;
    }

    static int solve(int N, int D, int C, int[] arr) {
        // binary search lowest
        int lowerBound;
        {
            int low = 0, tooHigh = D+1;
            while (low + 1 < tooHigh) {
                int mid = low + (tooHigh - low) / 2;
                boolean isLowEnough = canLowerBoundWork(mid, N, C, arr);
                if (isLowEnough) {
                    low = mid;
                }
                else {
                    tooHigh = mid;
                }
            }
            lowerBound = low;
        }
        // binary search highest
        int upperBound;
        {
            int tooLow = -1, high = D;
            while (tooLow + 1 < high) {
                int mid = tooLow + (high - tooLow) / 2;
                boolean isHighEnough = canUpperBoundWork(mid, N, C, arr);
                if (isHighEnough) {
                    high = mid;
                }
                else {
                    tooLow = mid;
                }
            }
            upperBound = high;
        }
        int ans = Math.max(0, upperBound - lowerBound);
        return ans;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int N = in.nextInt();
        int D = in.nextInt();
        int C = in.nextInt();
        int[] arr = new int[N];
        for(int n=0;n<N;n++) {
            arr[n] = in.nextInt();
        }

        int solution = solve(N,D,C,arr);

        System.out.println(solution);
    }
}