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#include "message.h"
#include "krazki.h"
#include <vector>
#include <cstdio>
using namespace std;

#define LL long long
#define INF 3000000000000000000LL

int n, m;
int numberOfNodes;
int myNodeId;
int first, last;
LL mi = INF;
LL ma = INF;
vector<LL> data;

#define MEMORIZE_EXP (24)
#define MEMORIZE_FROM (29 - MEMORIZE_EXP)
#define MEMORIZE_OFFSET (mem.size() / 2)
int testCounter = 0;
int memStart = -1;
vector<LL> mem;

int spreader = 0;

inline LL diameter(int i){
    if(testCounter >= MEMORIZE_FROM){
        int a = i + MEMORIZE_OFFSET - memStart;
        if(a >= 0 && a < int(mem.size())){
            if(mem[a] != 0)return mem[a];
            mem[a] = DiscDiameter(i);
            return mem[a];
        }
    }
    return DiscDiameter(i);
}

bool test(int s){
    ++testCounter;
    if(testCounter == MEMORIZE_FROM){
        mem.resize(data.size() + (1 << MEMORIZE_EXP), 0);
        memStart = m + s - (first + last) / 2;
    }
    for(int a=max(first, s); a<last; ++a){
        if(a-s >= m)break;
        if(diameter(m - a + s) > data[a - first]){
            return 0;
        }
    }
    return 1;
}

bool testServer(int s){
    if(spreader == 0){
        for(int a=1; a<numberOfNodes; ++a){
            PutInt(a, s);
            Send(a);
        }
    }else{
        PutInt(spreader, s);
        Send(spreader);
    }
    spreader = (spreader + 1) % numberOfNodes;

    bool b = test(s);
    for(int a=1; a<numberOfNodes; ++a){
        Receive(a);
        char c = GetChar(a);
        b &= c;
    }
    return b;
}

int main(){
    n = PipeHeight();
    m = NumberOfDiscs();
    numberOfNodes = NumberOfNodes();
    myNodeId = MyNodeId();

    first = (((LL)myNodeId) * n) / numberOfNodes;
    last = (((LL)myNodeId + 1) * n) / numberOfNodes;
    data.resize(last - first);

    for(int a=first; a<last; ++a){
        LL r = HoleDiameter(a + 1);
        mi = min(mi, r);
        data[a - first] = mi;
    }

    if(myNodeId != 0){
        PutLL(0, mi);
        Send(0);
        Receive(0);
        ma = GetLL(0);
    }else{
        LL q = mi;
        for(int a=1; a<numberOfNodes; ++a){
            PutLL(a, q);
            Send(a);

            Receive(a);
            q = min(q, GetLL(a));
        }
    }
    for(int a=first; a<last; ++a){
        if(data[a - first] > ma){
            data[a - first] = ma;
        }
    }

    if(myNodeId != 0){
        while(1){
            int i = 0;
            if(myNodeId != spreader){
                Receive(spreader);
                i = GetInt(spreader);
            }else{
                Receive(0);
                i = GetInt(0);
                for(int a=1; a<numberOfNodes; ++a){
                    if(a != myNodeId){
                        PutInt(a, i);
                        Send(a);
                    }
                }
            }

            if(i == -1)break;
            PutChar(0, test(i));
            Send(0);

            spreader = (spreader + 1) % numberOfNodes;
        }
    }else{
        int best = -1;
        int left = 0;
        int right = n-m;
        while(left <= right){
            int s = (left + right) / 2;
            if(testServer(s)){
                best = s;
                left = s + 1;
            }else{
                right = s - 1;
            }
        }
        if(spreader == 0){
            for(int a=1; a<numberOfNodes; ++a){
                PutInt(a, -1);
                Send(a);
            }
        }else{
            PutInt(spreader, -1);
            Send(spreader);
        }
        spreader = (spreader + 1) % numberOfNodes;

        printf("%d", best + 1);
    }

    return 0;
}