If-else statement by user input in serial monitor

Question

Hello everyone, i try to do if-else statement by using a user input in serial monitor. but everytime i enter a number on serial monitor, the print is not what i code. anyone please help, thank you 
 
 char value0; 
 void setup (){ Serial.begin(9600); delay(200); Serial.println("Enter Number: "); } 
 void loop() { if( Serial.available()) { value0 = Serial.read(); if((value0 > '39') && (value0 < '151')) { Serial.println("Play song 1"); } else { Serial.println("Next song"); } } }

Okamiya Yuuki · Accepted Answer

I give you a sample code. When you hit number and enter, serial monitor will display either. 
 
String command; 
 
void setup() { 
 Serial.begin(9600); 
} 
 
void loop() { 
 if(Serial.available()){ 
 command = Serial.readStringUntil('
'); 
 int value = command.toInt(); 
 if((value > 39) && (value < 151)){ 
 Serial.println("Play song 1"); 
 } 
 else{ 
 Serial.println("Next song"); 
 } 
 } 
}