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# Count ordered pairs with product less than N in C++

We are given a number N. The goal is to find ordered pairs of positive numbers such that their product is less than N.

We will do this by starting from i=1 to i<N and j=1 to (i*j)<N. Then increment count.

Let’s understand with examples.

**Input**

N=4

**Output**

Ordered pairs such that product is less than N:5

**Explanation**

Pairs will be (1,1) (1,2) (1,3) (2,1) (3,1)

**Input**

N=100

**Output**

Ordered pairs such that product is less than N: 473

**Explanation**

Pairs will be (1,1) (1,2) (1,3)....(97,1), (98,1), (99,1). Total 473.

## Approach used in the below program is as follows

We take integer N.

Function productN(int n) takes n and returns the count of ordered pairs with product < n

Take the initial variable count as 0 for pairs.

Traverse using two for loops for making pairs.

Start from i=1 to i<n. And j=1 to (i* j)<n.

Increment count by 1.

At the end of all loops count will have a total number of such pairs.

Return the count as result.

## Example

#include <bits/stdc++.h> using namespace std; int productN(int n){ int count = 0; for (int i = 1; i < n; i++){ for(int j = 1; (i*j) < n; j++) { count++; } } return count; } int main(){ int N = 6; cout <<"Ordered pairs such that product is less than N:"<<productN(N); return 0; }

## Output

If we run the above code it will generate the following output −

Ordered pairs such that product is less than N:10

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