遞歸求sum

#include <iostream>

using namespace std;

int sum1=0;

int sum(int n,int m)

{

if(m!=n)

{

sum1=sum(n,m-1)+m;

}

if(m==n)

{

sum(n,m-1)=n;

}

}

int main()

{

cout<<sum(3,5);

}