upsolve: solution of problem C in Codechef Sept Starters 2021

Author: NirmalSilwal

Codechef/StartersSept2021/C.java

@@ -0,0 +1,85 @@
+package StartersSept2021;
+
+import java.io.PrintWriter;
+import java.io.BufferedReader;
+import java.io.InputStreamReader;
+import java.io.IOException;
+import java.util.StringTokenizer;
+
+public class C {
+
+	public static void main(String[] args) {
+
+		FastReader sc = new FastReader();
+		PrintWriter out = new PrintWriter(System.out);
+
+		int t = sc.nextInt();
+
+		for (int tt = 0; tt < t; tt++) {
+
+			long N = sc.nextLong();
+			long S = sc.nextLong();
+
+			long totalSum = (N * (N + 1)) / 2;
+			long diff = totalSum - S;
+
+			if (diff >= 1 && diff <= N)
+				System.out.println(diff);
+			else
+				System.out.println(-1);
+
+		}
+
+		out.close();
+	}
+
+	static class FastReader {
+		BufferedReader br;
+		StringTokenizer st;
+
+		FastReader() {
+			br = new BufferedReader(new InputStreamReader(System.in));
+		}
+
+		String next() {
+			while (st == null || !st.hasMoreElements()) {
+				try {
+					st = new StringTokenizer(br.readLine());
+				} catch (IOException e) {
+					e.printStackTrace();
+				}
+			}
+			return st.nextToken();
+		}
+
+		int nextInt() {
+			return Integer.parseInt(next());
+		}
+
+		long nextLong() {
+			return Long.parseLong(next());
+		}
+
+		double nextDouble() {
+			return Double.parseDouble(next());
+		}
+
+		String nextLine() {
+			String str = "";
+			try {
+				str = br.readLine();
+			} catch (IOException e) {
+				e.printStackTrace();
+			}
+			return str;
+		}
+
+		int[] readArray(int n) {
+			int[] temparr = new int[n];
+			for (int i = 0; i < n; i++) {
+				temparr[i] = nextInt();
+			}
+			return temparr;
+		}
+	}
+}