#include<stdio.h>

int main(){
    int units;
    float bill = 0.0;
    
    if(scanf("%d",&units)!= 1){
        printf("Invalid input");
        return 0;
    }
    
    
    if(units < 0){
        printf("Invalid input");
        return 0;
    }
    
    if(units <= 100){
        bill = units*0.10;
    }
    else if(units <= 200){
        bill =(100*0.10)+(units-100)*0.15;
    }
    else{
        bill = 100*0.10+100*0.15+(units - 200)*0.20;
    }
    
    print("%.2f."bill);
    
    return 0;
}