#include <iostream>
#include <vector>
using namespace std;

int main() {
    vector<vector<int>> nums = {
        {1,4,6,3,8,2},
        {3,5,1,9,7,4},
        {5,2,7,5,9,1}
    };

    int l = 2, r = 4;   // Sum from index 2 to 4 (inclusive)

    // Prefix sum for each row
    vector<vector<int>> prefix(nums.size());

    for (int i = 0; i < nums.size(); i++) {
        prefix[i].resize(nums[i].size());

        prefix[i][0] = nums[i][0];

        for (int j = 1; j < nums[i].size(); j++) {
            prefix[i][j] = prefix[i][j - 1] + nums[i][j];
        }
    }

    // Answer queries
    for (int i = 0; i < nums.size(); i++) {
        int sum;
        if (l == 0)
            sum = prefix[i][r];
        else
            sum = prefix[i][r] - prefix[i][l - 1];

        cout << "Sum: " << sum << endl;
    }

    return 0;
}