Gap

input/code.cpp: In function 'll findGap(int, int)':
input/code.cpp:16:11: error: expected ';' before 'std'
       res std:: max(res,b-a);
           ^~~
input/code.cpp:16:29: warning: statement has no effect [-Wunused-value]
       res std:: max(res,b-a);
                             ^
input/code.cpp:7:6: warning: unused variable 'start' [-Wunused-variable]
   ll start = 0;
      ^~~~~

#include <bits/stdc++.h>
#include "gap.h"
typedef long long ll;
#define MAX (1e18)
ll findGap(int t,int n) {
  ll res = 0;
  ll start = 0;
  ll min = 0, max = 0;
  (void) MinMax(0,MAX,&min, &max);
  ll a = min;
  ll b = max;
  for (;;) {
    ll o = b-1;
    (void) MinMax(0,MAX,&a, &o);
    if (a == o) {
      res std:: max(res,b-a);
      break;
    }
    res = std:: max(res, b-o);
    b = o;
  }
  return res;
}