#include<bits/stdc++.h> using namespace std; //定义函数 int sum(int a,int b){ int s = 0; for(int i=a;i<=b;i++){ s += i; } return s;//返回值。 } int main(){ cout<<sum(1,10)<<endl; cout<<sum(20,30)<<endl; cout<<sum(35,45)<<endl; }