#include<stdio.h>#include<string.h>#define MAXD 110#define INF 1000000000#define MAX 1001int yM[MAXD], visy[MAXD], visx[MAXD];int G[MAXD][MAXD], N, M, A[MAXD], B[MAXD], slack;void init(){int i, a, b, temp;    memset(G, 0, sizeof(G));for(i = 0; i < M; i ++)    {        scanf("%d%d%d", &a, &b, &temp);        a --;        b --;if(!G[a][b] || MAX - temp > G[a][b])            G[a][b] = MAX - temp;    }}int searchpath(int u){int v, temp;    visx[u] = 1;for(v = 0; v < N; v ++)if(G[u][v] && !visy[v])        {            temp = A[u] + B[v] - G[u][v];if(temp == 0)            {                visy[v] = 1;if(yM[v] == -1 || searchpath(yM[v]))                {                    yM[v] = u;return 1;                }            }else if(temp < slack)                slack = temp;        }return 0;}int EK(){int i, j;for(i = 0; i < N; i ++)    {        A[i] = 0;for(j = 0; j < N; j ++)if(G[i][j] && G[i][j] > A[i])                A[i] = G[i][j];    }    memset(B, 0, sizeof(B));    memset(yM, -1, sizeof(yM));for(i = 0; i < N; i ++)    {for(;;)        {            slack = INF;            memset(visx, 0, sizeof(visx));            memset(visy, 0, sizeof(visy));if(searchpath(i))break;if(slack == INF)return 0;for(j = 0; j < N; j ++)            {if(visx[j])                    A[j] -= slack;if(visy[j])                    B[j] += slack;            }        }    }return 1;}void printresult(){int i, res = 0;for(i = 0; i < N; i ++)        res += MAX - G[yM[i]][i];    printf("%d\n", res);}int main(){int i, j;while(scanf("%d%d", &N, &M) != EOF)    {        init();if(EK())            printresult();else            printf("-1\n");    }return 0;    }