#include <bits/stdc++.h>
 
using namespace std;
 
// Structure for an item which stores weight and
// corresponding value of Item
struct Item {
    int value, weight;
 
    // Constructor
    Item(int value, int weight)
    {
        this->value = value;
        this->weight = weight;
    }
};
 
// Comparison function to sort Item according to val/weight
// ratio
bool cmp(struct Item a, struct Item b)
{
    double r1 = (double)a.value / (double)a.weight;
    double r2 = (double)b.value / (double)b.weight;
    return r1 > r2;
}
 
// Main greedy function to solve problem
double fractionalKnapsack(int W, struct Item arr[], int N)
{
    //    sorting Item on basis of ratio
    sort(arr, arr + N, cmp);
 
    double finalvalue = 0.0; // Result (value in Knapsack)
 
    // Looping through all Items
    for (int i = 0; i < N; i++) {
        // If adding Item won't overflow, add it completely
        if (arr[i].weight <= W) {
            W -= arr[i].weight;
            finalvalue += arr[i].value;
        }
 
        // If we can't add current Item, add fractional part
        // of it
        else {
            finalvalue
                += arr[i].value
                   * ((double)W / (double)arr[i].weight);
            break;
        }
    }
 
    // Returning final value
    return finalvalue;
}
 
// Driver's code
int main()
{
    int W = 50; //    Weight of knapsack
    Item arr[] = { { 60, 10 }, { 100, 20 }, { 120, 30 } };
 
    int N = sizeof(arr) / sizeof(arr[0]);
 
    // Function call
    cout << "Maximum value we can obtain = "
         << fractionalKnapsack(W, arr, N);
    return 0;
}