Update app.py

app.py

@@ -274,7 +274,7 @@ if __name__=='__main__':
     It is a app for predicting Rf values of a compound under given eluents in TLC.\n
     input: smiles of one compound, such as CC(OCC)=O; \n
            the ratio of five solvents (example: 20 1 0 0 0 for PE:EA=20:1)\n
-    output: the predicted Rf value.\n
+    output: the predicted Rf value.\n\n
     
     ## Citation\n
     Welcome to cite our work:\n