Multiplication of Matrices

How can I finish this matrix multiplication code with an accumulator?

MatrizA=3x4 - MatrizB=4x3 - Resultante=3x3 :

for (j=o; j<n-1;j++){
        for (i=0; i<m-1;i++){
            Acumulador=0;

            for (k=0; k<=P-1 ; k++){
                acumulador= MatrizA[ i][k]* MatrizB[k][i]+ acumulador;
            }

            R-[i][j]=Acumulador;
        }
 }