[Codeforces #188] Tutorial

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Codeoforces #188 传送门

A:

先全转为正数，后面就全是指数级增长了

#include <bits/stdc++.h>

using namespace std;
#define X first
#define Y second
typedef long long ll;
typedef pair<int,int> P;
ll x,y,m,res;

int main()
{
    cin>>x>>y>>m;
    if(max(x,y)<m&&max(x,y)<=0) 
        return puts("-1"),0;
    
    while(x<m&&y<m)
    {
        if(x>y) swap(x,y);
        ll t=(y-x)/y+1;
        res+=t;x+=t*y;
    }
    cout<<res;
    return 0;
}

Problem A