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  1. #include<bits/stdc++.h>
  2. using namespace std;
  3.  
  4. long long n,m,t;
  5.  
  6. int main() {
  7.  
  8.     cin>>t;
  9.     while(t--) {
  10.         scanf("%lld %lld",&n,&m);
  11.  
  12.         if(n==1) {
  13.             if(m==0)
  14.                 puts("0");
  15.             else if(m==1)
  16.                 puts("1");
  17.             else
  18.                 puts("-1");
  19.  
  20.             continue;
  21.         }
  22.  
  23.         if(m>=n-1 && m<= n*(n-1)/2+n) {
  24.  
  25.             if(m-(n-1)>n) {
  26.  
  27.                 if(m==n*2)
  28.                     puts("3");
  29.                 else{
  30.  
  31.                    int ans;
  32.                    long long dif=m-n*2;
  33.                    long long val=n/2;
  34.  
  35.                    if(n%2==0){
  36.                      ans=3+ceil((double)dif/val);
  37.                    }else{
  38.  
  39.                      long long frac1=dif/(2*val+1);
  40.                      long long frac2=ceil(((double)m-(n*2+frac1*(2*val+1)))/val);
  41.                      ans=frac1*2+3+frac2;
  42.                    }
  43.  
  44.                    printf("%d\n",ans);
  45.  
  46.                 }
  47.  
  48.  
  49.             } else {
  50.  
  51.                 if(m-(n-1)==0){
  52.                     if(n==2)
  53.                      puts("1");
  54.                     else
  55.                     puts("2");
  56.                 }
  57.                 else if(m-(n-1)-2>0)
  58.                     puts("3");
  59.                 else
  60.                     puts("2");
  61.  
  62.             }
  63.  
  64.  
  65.         } else {
  66.             puts("-1");
  67.         }
  68.  
  69.  
  70.     }
  71.  
  72.  
  73.     return 0;
  74. }
  75. /*
  76. 22 242
  77. ans=22
  78. my output=21
  79.  
  80. */
  81.  
Success #stdin #stdout 0s 4400KB
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https://ideone.com/3vklml
language:
C++14 (gcc 8.3)
created:
5 years ago
visibility:
public

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