C language "recursive series": recursive implementation of 1+2+3++ n

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include<string.h>
int fun(int m)
{
    
	int w;
	if (m==1)
		w = 1;
	else
		w=fun(m - 1) + m;
	return w;
}
int main()
{
    
	int n;
	scanf("%d", &n);
	printf("1+2+...+%d=%d\n",n,fun(n));
	return 0;
}

analysis ：