func_code_string: #include <bits/stdc++.h>   const int N = 65550;   int ru[N], sum[N];   int n;   int s[N], t[N], cc = 0;   int main() {     int i;     scanf( %d , &n);     for (i = 0; i < n; i++) scanf( %d%d , &ru[i], &sum[i]);     for (i = 0; i < n; i++) {       int now = i;       while (ru[now] == 1) {         cc++;         s[cc] = now;         t[cc] = sum[now];         ru[now]--;         ru[sum[now]]--;         sum[sum[now]] ^= now;         now = sum[now];       }     }     printf( %d n , cc);     for (i = 1; i <= cc; i++) printf( %d %d n , s[i], t[i]);     return 0;   }   