Little Boy And His Toy

#include<stdio.h>

int main()
{
    int n;
    scanf("%d",&n);
    int arr[n];
    for(int i = 0 ; i < n ; i ++){
        scanf("%d",&arr[i]);
    }
    int sum = 0;
    int cnt = 0;
    for(int i = 1 ; sum <= n ; i ++){
        sum += i;
        cnt++;
    }
    printf("%d",cnt-1);
    return 0;
}