#include <iostream>

#include <cstring>

#include <cstdio>

#include <algorithm>

using namespace std;

const int maxn =  + ;

const int inf = 0x3f3f3f3f;

bool visr[maxn], visl[maxn];

int n, delta, w[maxn][maxn], lx[maxn], ly[maxn], lft[maxn];

inline bool match( int x ){

    visl[x] = ;

    for( int y=; y<=n; y++ )

        if( lx[x]+ly[y]==w[x][y] && !visr[y] ){

            visr[y] = ;

            if( !lft[y] || match(lft[y]) ){

                lft[y] = x;

                return ;

            }

        }

    return ;

}

inline void update(){

    for( int i=; i<=n; i++ ) if( visl[i] )

        for( int j=; j<=n; j++ ) if( !visr[j] )

            delta = min( delta, lx[i]+ly[j]-w[i][j] );

    for( int i=; i<=n; i++ ){

        if( visl[i] ) lx[i] -= delta;

        if( visr[i] ) ly[i] += delta;

    }

}

inline int KM(){

    for( int i=; i<=n; i++ ){

        lft[i] = ly[i] = ;

        lx[i] = -inf;

        for( int j=; j<=n; j++ )

            lx[i] = max(lx[i], w[i][j]);

    }

    for( int i=; i<=n; i++ ){

        while(){

            delta = inf;

            memset( visr, , sizeof(visr) );

            memset( visl, , sizeof(visl) );

            if( match(i) ) break;

            update();

        }

    }

    int res = ;

    for( int i=; i<=n; i++ ) res += w[lft[i]][i];

    return res;

}

int main(){

    // freopen("in.txt", "r", stdin);

    while( ~scanf("%d", &n) && n ){

        for( int i=; i<=n; i++ )

            for( int j=; j<=n; j++ ) w[i][j] = -inf;        //不能使用memset( w, -inf, sizeof(w) );

        for( int i=; i<=n; i++ ){

            int j;

            while( ~scanf("%d", &j) && j ){

                int d;

                scanf("%d", &d);

                w[i][j] = max( -d, w[i][j] );

            }

        }

        int ans = KM();

        if( -ans>=inf ) puts("N");

        else printf("%d\n", -ans);

    }

    return ;

}