#include <bits/stdc++.h>
using namespace std;
namespace FastIO {
	struct IO {
	    char ibuf[(1 << 20) + 1], *iS, *iT, obuf[(1 << 20) + 1], *oS;
	    IO() : iS(ibuf), iT(ibuf), oS(obuf) {} ~IO() { fwrite(obuf, 1, oS - obuf, stdout); }
		#if ONLINE_JUDGE
		#define gh() (iS == iT ? iT = (iS = ibuf) + fread(ibuf, 1, (1 << 20) + 1, stdin), (iS == iT ? EOF : *iS++) : *iS++)
		#else
		#define gh() getchar()
		#endif
		inline bool eof (const char &ch) { return ch == ' ' || ch == '\n' || ch == '\r' || ch == 't' || ch == EOF; }
	    inline long long read() {
	        char ch = gh();
	        long long x = 0;
	        bool t = 0;
	        while (ch < '0' || ch > '9') t |= ch == '-', ch = gh();
	        while (ch >= '0' && ch <= '9') x = (x << 1) + (x << 3) + (ch ^ 48), ch = gh();
	        return t ? ~(x - 1) : x;
	    }
	    inline void read (char *s) {
	    	char ch = gh(); int l = 0;
	    	while (eof(ch)) ch = gh();
	    	while (!eof(ch)) s[l++] = ch, ch = gh();
	    }
	    inline void read (double &x) {
	    	char ch = gh(); bool t = 0;
	    	while (ch < '0' || ch > '9') t |= ch == '-', ch = gh();
	    	while (ch >= '0' && ch <= '9') x = x * 10 + (ch ^ 48), ch = gh();
	    	if (ch != '.') return t && (x = -x), void(); ch = gh();
	    	for (double cf = 0.1; '0' <= ch && ch <= '9'; ch = gh(), cf *= 0.1) x += cf * (ch ^ 48);
	    	t && (x = -x);
	    }
	    inline void pc (char ch) {
	    	#ifdef ONLINE_JUDGE
	    	if (oS == obuf + (1 << 20) + 1) fwrite(obuf, 1, oS - obuf, stdout), oS = obuf; 
	    	*oS++ = ch;
	    	#else
	    	putchar(ch);
	    	#endif
		}
		template<typename _Tp>
	    inline void write (_Tp x) {
	    	static char stk[64], *tp = stk;
	    	if (x < 0) x = ~(x - 1), pc('-');
			do *tp++ = x % 10, x /= 10;
			while (x);
			while (tp != stk) pc((*--tp) | 48);
	    }
	    inline void write (char *s) {
	    	int n = strlen(s);
	    	for (int i = 0; i < n; i++) pc(s[i]);
	    }
	} io;
	inline long long read () { return io.read(); }
	template<typename Tp>
	inline void read (Tp &x) { io.read(x); }
	template<typename _Tp>
	inline void write (_Tp x) { io.write(x); }
}
using namespace FastIO;
#define int long long 
const int maxn=305,inf=1e18;
int n,m,k;
vector< tuple<int,int,int> > G[maxn];
bool col[maxn];
int f[6][maxn][maxn],up[maxn],vp[maxn],wp[maxn],h[maxn][maxn][3],idh[maxn][maxn][3];
mt19937 rnd(231232134);
void init1()
{
    for(int i=1;i<=n;i++)for(int j=1;j<=n;j++)f[1][i][j]=-inf;
    for(int i=1;i<=n;i++)f[1][i][i]=0;
}
void init2()
{
    for(int i=1;i<=n;i++)for(int j=1;j<=n;j++)f[2][i][j]=-inf;
    for(int i=1;i<=m;i++)
        if(col[up[i]]==col[vp[i]])f[2][up[i]][vp[i]]=f[2][vp[i]][up[i]]=max(f[2][up[i]][vp[i]],wp[i]);
}
inline void init3()
{
    for(int i=1;i<=n;i++)for(int j=1;j<=n;j++)f[3][i][j]=-inf;
    for(int i=1;i<=n;i++)
        for(auto [j,w1,id1]:G[i])
            for(auto [k,w2,id2]:G[i])
                if(col[i]==col[j]&&col[i]==col[k]&&j!=k)
                    f[3][k][j]=f[3][j][k]=max(f[3][j][k],w1+w2);
}
inline void init4()
{
    for(int i=1;i<=n;i++)for(int j=1;j<=n;j++)f[4][i][j]=-inf;
    for(int i=1;i<=m;i++)
    {
        if(col[up[i]]!=col[vp[i]])continue;
        for(auto [j,w1,id1]:G[up[i]])
            for(auto [k,w2,id2]:G[vp[i]])
                if(col[up[i]]==col[j]&&col[vp[i]]==col[k]&&up[i]!=k&&vp[i]!=j&&k!=j)
                    f[4][j][k]=f[4][k][j]=max(f[4][j][k],w1+w2+wp[i]);
    }
}
inline void upd(int v,int id,int i,int j)
{for(int t=0;t<3;t++)if(v>h[i][j][t]){swap(v,h[i][j][t]);swap(id,idh[i][j][t]);}}
inline int findminsec(int idn1,int idn2,int i,int j)
{for(int t=0;t<3;t++)if(idn1!=idh[i][j][t]&&idn2!=idh[i][j][t])return h[i][j][t];return -inf;}
inline void init5()
{
    for(int i=1;i<=n;i++)for(int j=1;j<=n;j++)f[5][i][j]=h[i][j][0]=h[i][j][1]=h[i][j][2]=-inf;
    for(int i=1;i<=n;i++)
        for(auto [j,w1,id1]:G[i])
            for(auto [k,w2,id2]:G[i])
                if(col[i]==col[j]&&col[i]==col[k]&&j!=k)
                {
                    upd(w1+w2,i,j,k);
                    upd(w1+w2,i,k,j);
                }
    for(int i=1;i<=m;i++)
        for(int j=1;j<=m;j++)
        {
            if(col[up[i]]!=col[vp[i]]||col[up[i]]!=col[up[j]]||col[up[i]]!=col[vp[j]]||col[up[j]]!=col[vp[j]]||up[i]==up[j]||up[i]==vp[j]||vp[i]==up[j]||vp[i]==vp[j])continue;
            f[5][up[i]][vp[j]]=max(f[5][up[i]][vp[j]],wp[i]+wp[j]+findminsec(up[i],vp[j],vp[i],up[j]));
            f[5][up[i]][up[j]]=max(f[5][up[i]][up[j]],wp[i]+wp[j]+findminsec(up[i],up[j],vp[i],vp[j]));
            f[5][vp[i]][vp[j]]=max(f[5][vp[i]][vp[j]],wp[i]+wp[j]+findminsec(vp[i],vp[j],up[i],up[j]));
            f[5][vp[i]][up[j]]=max(f[5][vp[i]][up[j]],wp[i]+wp[j]+findminsec(vp[i],up[j],up[i],vp[j]));
        }
}
signed main()
{
    n=read(),m=read(),k=read();
    for(int i=1;i<=m;i++)
        up[i]=read(),vp[i]=read(),wp[i]=read();
    for(int i=1;i<=m;i++)
    {
        G[up[i]].push_back({vp[i],wp[i],i});
        G[vp[i]].push_back({up[i],wp[i],i});
    }
    int t1=k/2,t2=k-t1,ans=-inf;
    if(k==3)
    {
        init2();
        for(int i=1;i<=m;i++)
            for(int j=1;j<=n;j++)
                if(j!=up[i]&&j!=vp[i])
                    ans=max(ans,wp[i]+f[2][up[i]][j]+f[2][vp[i]][j]);
    }
    else
    for(int sr=1;sr<=1000;sr++)
    {
        for(int i=1;i<=n;i++)col[i]=rnd()%2;
        if(t1==1||t2==1)init1();
        if(t1==2||t2==2)init2();
        if(t1==3||t2==3)init3();
        if(t1==4||t2==4)init4();
        if(t1==5||t2==5)init5();
        for(int i=1;i<=m;i++)
            for(int j=1;j<=m;j++)
            {
                if(up[i]!=up[j]&&up[i]!=vp[j]&&vp[i]!=up[j]&&vp[i]!=vp[j])
                {
                    
                    if(col[up[i]]==0&&col[vp[i]]==1&&col[up[j]]==0&&col[vp[j]]==1)
                        ans=max(ans,f[t1][up[i]][up[j]]+f[t2][vp[i]][vp[j]]+wp[i]+wp[j]);
                    if(col[up[i]]==0&&col[vp[i]]==1&&col[vp[j]]==0&&col[up[j]]==1)
                        ans=max(ans,f[t1][up[i]][vp[j]]+f[t2][vp[i]][up[j]]+wp[i]+wp[j]);
                    if(col[vp[i]]==0&&col[up[i]]==1&&col[up[j]]==0&&col[vp[j]]==1)
                        ans=max(ans,f[t1][vp[i]][up[j]]+f[t2][up[i]][vp[j]]+wp[i]+wp[j]);
                    if(col[vp[i]]==0&&col[up[i]]==1&&col[vp[j]]==0&&col[up[j]]==1)
                        ans=max(ans,f[t1][vp[i]][vp[j]]+f[t2][up[i]][up[j]]+wp[i]+wp[j]);
                }
            }
    }
    if(ans>0)printf("%lld\n",ans);
    else puts("impossible");
}
/*
6 13 3
2 1 99999998
3 1 99999998
3 2 100000000
4 1 99999998
4 2 100000000
4 3 99999998
5 1 99999999
5 2 99999998
5 3 99999998
5 4 99999998
6 1 99999998
6 2 99999998
6 3 99999998
*/