diff --git a/Lectures_my/EMPP/2016/Lecture4/Exercises/Error_propagation/err.py b/Lectures_my/EMPP/2016/Lecture4/Exercises/Error_propagation/err.py
new file mode 100644
index 0000000..00c1615
--- /dev/null
+++ b/Lectures_my/EMPP/2016/Lecture4/Exercises/Error_propagation/err.py
@@ -0,0 +1,42 @@
+from ROOT import *
+import sys
+
+def main(argv):
+    NTOYS=100000
+    SEED=1000
+    
+    r=float(argv[1])
+    r_err=float(argv[2])
+
+    rand = TRandom(SEED)
+   
+    r_list=[]
+    rsqr_list=[]
+    
+    print 'aaa'
+
+    hist_r = TH1D("r", "r", 100, r-5.*r_err, r+5*r_err)
+    hist_r2= TH1D("1/r2", "1/r2", 100, 1/((r-10*r_err)*(r-10*r_err)), 1/((r+10*r_err)*(r+10*r_err))) 
+
+    for i in range(NTOYS):
+        tmp=rand.Gaus(r,r_err)
+        
+        hist_r.Fill(tmp)
+        hist_r2.Fill(1./(tmp*tmp))
+        
+    
+    c1=TCanvas("c1", "c1", 1200, 600)
+    c1.Divide(2,1)
+    c1.cd(1)
+    hist_r.Draw()
+    hist_r.Fit('gaus')
+    c1.cd(2)
+    hist_r2.Draw()
+    hist_r2.Fit('gaus')
+    c1.SaveAs("result.png")
+
+
+
+
+if __name__ == "__main__":
+    main(sys.argv)