diff --git a/src/solver/Main.java b/src/solver/Main.java
index 4404714..54b44bf 100644
--- a/src/solver/Main.java
+++ b/src/solver/Main.java
@@ -1,7 +1,197 @@
-package solver;
+import java.util.*;
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.FileWriter;
+import java.io.IOException;
+/**
+i - неизвестная, j - уравнение
+*/
+public class fourth {
+	public static void main(String[] args) {
+		File file = new File("in.txt");
+		try(Scanner scanner = new Scanner(file)) {
+			int n = scanner.nextInt();
+			int m = scanner.nextInt();
+			// n - число неизвестных, m - число уравнений
+			double[] line = new double[n + 1];
+			Row[] row = new Row[m];
+			for (int j = 0; j < m; j++) 
+			{	
+				for (int i = 0; i <= n; i++){line[i] = scanner.nextDouble();}
+				row[j] = new Row(n, line);
+			}
+			Matrix matrix = new Matrix(row, n, m);
+			matrix.steppedViewDown();
+		} catch (FileNotFoundException e) {
+			System.out.println("I hope that never happen");
+		}
+	}
+}
 
-public class Main {
-    public static void main(String[] args) {
-        System.out.print("Hello world!");
-    }
-}
\ No newline at end of file
+class Row {
+	int N;
+	// N - число неизвестных
+	double[] line = new double[N];
+	public Row(int N, double[] row) {
+		this.line = Arrays.copyOf(row, N + 1);
+		this.N = N;
+	}
+
+	double getValue(int i) {
+		return this.line[i];
+	}
+
+	void add(Row other) {
+		for (int i = 0; i <= this.N; i++) {
+			this.line[i] += other.line[i];
+		}
+	}
+	void mul(double num) {
+		for (int i = 0; i <= this.N; i++) {
+			this.line[i] = this.line[i] * num;
+		}
+	}
+
+	String getString() {
+		return Arrays.toString(this.line);
+	}
+}
+
+class Matrix {
+	int N;
+	int M;
+	Row[] rows = new Row[1];
+	public Matrix(Row[] row, int n, int m) {
+		this.rows = row;
+		this.N = n;
+		this.M = m;
+	}
+// true - ненулевое
+	boolean checkValue(int i, int j) {  
+		return (this.rows[j].getValue(i) == 0 ? false: true);
+	}
+
+
+	String resetAllDown(int i, int j) {
+		String s = "";
+		double coef = this.rows[j].getValue(i);		
+		this.rows[j].mul(1 / coef);
+		s = (1 / coef) +  "*R" + (j + 1) + " -> R" + (j + 1) + "\n";
+		for (int k = j + 1; k < this.M; k++) {
+			coef = this.rows[k].getValue(i);
+			if (coef != 0) {
+				this.rows[k].mul( (-1) / coef);
+				this.rows[k].add(this.rows[j]);
+				s = s + (-1) / coef + "*R" + (k + 1) + " + R" + (j + 1) + " -> R" + (k + 1) + "\n";
+			}
+		}
+		return s;
+	}
+
+	String resetAllUp(int i, int j) {
+		String s = "";
+		double coef = this.rows[j].getValue(i);
+		this.rows[j].mul(1 / coef);
+		s = (1 / coef) +  "*R" + (j + 1) + " -> R" + (j + 1) + "\n";
+		for (int k = j - 1; k >= 0; k--) {
+			coef = this.rows[k].getValue(i);
+			if (coef != 0) {
+				this.rows[k].mul( (-1) / coef);
+				this.rows[k].add(this.rows[j]); 
+				s = s + (-1) / coef + "*R" + (k + 1) + " + R" + (j + 1) + " -> R" + (k + 1) + "\n";
+			}
+		}
+		return s;
+	}
+
+	void steppedViewDown () {
+		int j = 0;
+		int i = 0;
+		String s = "";
+		s += "start solving the equation\n";
+		s += "Rows manipulation\n";
+		for (; i <= this.N && j < this.M; i++) {
+			if (this.checkValue(i, j)) {
+				s += this.resetAllDown(i, j);
+				j += 1;
+			}
+			else { //пробегаю вниз. Если есть ненулевой - свапаю, если нет - перехожу к след i и j;
+				for (int k = j + 1; k < this.M; k++) {
+					if (this.checkValue(i, k)) {
+						this.swap(i, k);
+						s = s + "Swap R" + (i + 1) + " with R" + (k + 1) + "\n";
+					}
+				}
+				if (!this.checkValue(i, j)) {
+					i += 1;
+				}
+				i -= 1;
+			}
+		}
+
+		if (j == 0) {
+			s += "infinity solutions\n";
+		}
+
+		else {
+			if (!this.checkNonzero(0, j - 1)) {
+				s += "no solutions\n";
+			}
+			else {
+				if (j != this.N) {
+					s += "infinity solutions\n";
+				}
+				else {
+					s += this.steppedViewUp();
+				}
+			}
+		}
+		File file = new File("out.txt");
+		try (FileWriter writer = new FileWriter(file)) {
+			writer.write(s);
+		} catch (IOException e) {
+			System.out.printf("Exception");
+		}
+	}
+
+	String steppedViewUp () {
+		String s = "";
+		for (int j = this.N - 1; j > 0; j--) {
+			s += this.resetAllUp(j, j);
+		}
+		s += this.solve();
+		return s;
+	}
+// true - есть ненулевой элемент помимо ответа
+	boolean checkNonzero(int i, int j) {
+		if (i < this.N - 1) {
+			return (this.checkNonzero(i + 1, j) || this.checkValue(i, j));
+		}
+		else {
+			return this.checkValue(i, j);
+		}
+	}
+
+	void swap(int i, int j) { 
+		Row row = this.rows[i];
+		this.rows[i] = this.rows[j];
+		this.rows[j] = row;
+	}
+	String getString() {
+		String s = "";
+		for (int i = 0; i < this.M; i++) {
+			s += this.rows[i].getString();
+		}
+		return s;
+	}
+	String solve () {
+		String s = "";
+		s += "The solution is: (";
+		for (int i = 0; i < this.N - 1; i++) {
+			s = s + this.rows[i].getValue(this.N) + ", ";
+		}
+		s = s + this.rows[this.N - 1].getValue(this.N) + ")\n";
+		return s;
+	}
+
+}