Given an array **arr[]** of **N** integers. The task is to find the sum of elements till the smallest index such that there are no even elements to the right of the index. **Note** that the array will have at least one even element.

**Examples:**

Input:arr[] = {2, 3, 5, 6, 3, 3}

Output:16

2 + 3 + 5 + 6 = 16

Input:arr[] = {3, 4}

Output:7

3 + 4 = 7

**Approach:** Find the index of the rightmost even element from the array and return the sum of all the elements starting from index 0 till the found index.

Below is the implementation of the above approach:

## C++

`// C++ implementation of the approach ` `#include <bits/stdc++.h> ` `using` `namespace` `std; ` ` ` `// Function to return the required sum ` `int` `smallestIndexsum(` `int` `arr[], ` `int` `n) ` `{ ` ` ` ` ` `// Starting from the last index ` ` ` `int` `i = n - 1; ` ` ` ` ` `// Skip all odd elements and find the ` ` ` `// index of the righmost even element ` ` ` `while` `(i >= 0 && arr[i] % 2 == 1) ` ` ` `i--; ` ` ` ` ` `// To store the requried sum ` ` ` `int` `sum = 0; ` ` ` `for` `(` `int` `j = 0; j <= i; j++) ` ` ` `sum += arr[j]; ` ` ` ` ` `return` `sum; ` `} ` ` ` `// Driver code ` `int` `main() ` `{ ` ` ` ` ` `int` `arr[] = { 2, 3, 5, 6, 3, 3 }; ` ` ` `int` `n = ` `sizeof` `(arr) / ` `sizeof` `(arr[0]); ` ` ` ` ` `cout << smallestIndexsum(arr, n); ` ` ` ` ` `return` `0; ` `} ` |

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## Java

`// Java implementation of the approach ` `class` `GFG ` `{ ` ` ` `// Function to return the required sum ` `static` `int` `smallestIndexsum(` `int` `arr[], ` `int` `n) ` `{ ` ` ` ` ` `// Starting from the last index ` ` ` `int` `i = n - ` `1` `; ` ` ` ` ` `// Skip all odd elements and find the ` ` ` `// index of the righmost even element ` ` ` `while` `(i >= ` `0` `&& arr[i] % ` `2` `== ` `1` `) ` ` ` `i--; ` ` ` ` ` `// To store the requried sum ` ` ` `int` `sum = ` `0` `; ` ` ` `for` `(` `int` `j = ` `0` `; j <= i; j++) ` ` ` `sum += arr[j]; ` ` ` ` ` `return` `sum; ` `} ` ` ` `// Driver code ` `public` `static` `void` `main(String[] args) ` `{ ` ` ` `int` `arr[] = { ` `2` `, ` `3` `, ` `5` `, ` `6` `, ` `3` `, ` `3` `}; ` ` ` `int` `n = arr.length; ` ` ` ` ` `System.out.println(smallestIndexsum(arr, n)); ` `} ` `} ` ` ` `// This code is contributed by 29AjayKumar ` |

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## Python3

`# Python3 implementation of the approach ` ` ` `# Function to return the required sum ` `def` `smallestIndexsum(arr, n): ` ` ` ` ` `# Starting from the last index ` ` ` `i ` `=` `n ` `-` `1` `; ` ` ` ` ` `# Skip all odd elements and find the ` ` ` `# index of the righmost even element ` ` ` `while` `(i >` `=` `0` `and` `arr[i] ` `%` `2` `=` `=` `1` `): ` ` ` `i ` `-` `=` `1` `; ` ` ` ` ` `# To store the requried sum ` ` ` `sum` `=` `0` `; ` ` ` `for` `j ` `in` `range` `(` `0` `, i ` `+` `1` `): ` ` ` `sum` `+` `=` `arr[j]; ` ` ` ` ` `return` `sum` `; ` ` ` `# Driver code ` `if` `__name__ ` `=` `=` `'__main__'` `: ` ` ` ` ` `arr ` `=` `[ ` `2` `, ` `3` `, ` `5` `, ` `6` `, ` `3` `, ` `3` `]; ` ` ` `n ` `=` `len` `(arr); ` ` ` ` ` `print` `(smallestIndexsum(arr, n)); ` ` ` `# This code is contributed by PrinciRaj1992 ` |

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## C#

`// C# implementation of the approach ` `using` `System; ` ` ` `class` `GFG ` `{ ` ` ` `// Function to return the required sum ` `static` `int` `smallestIndexsum(` `int` `[]arr, ` `int` `n) ` `{ ` ` ` ` ` `// Starting from the last index ` ` ` `int` `i = n - 1; ` ` ` ` ` `// Skip all odd elements and find the ` ` ` `// index of the righmost even element ` ` ` `while` `(i >= 0 && arr[i] % 2 == 1) ` ` ` `i--; ` ` ` ` ` `// To store the requried sum ` ` ` `int` `sum = 0; ` ` ` `for` `(` `int` `j = 0; j <= i; j++) ` ` ` `sum += arr[j]; ` ` ` ` ` `return` `sum; ` `} ` ` ` `// Driver code ` `static` `public` `void` `Main () ` `{ ` ` ` `int` `[]arr = { 2, 3, 5, 6, 3, 3 }; ` ` ` `int` `n = arr.Length; ` ` ` ` ` `Console.Write(smallestIndexsum(arr, n)); ` `} ` `} ` ` ` `// This code is contributed by ajit. ` |

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**Output:**

16

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