a+b对7取模就好了，如果结果是0就改为7

A.cpp

@@ -0,0 +1,14 @@
+//
+// Created by jal on 2019-04-01.
+//
+#include <bits/stdc++.h>
+using namespace std;
+int main(){
+    int a,b;
+    while(cin >> a >> b){
+        if(a == 0 && b == 0)break;
+        int c = (a+b)%7;
+        if(c==0)c=7;
+        cout << c<<endl;
+    }
+}