function solve( a , b ) {
// write code here
let m = a.length
let matrix = Array.from(new Array(m), ()=> new Array(m).fill(0))
for(let i = 0 ;i<m; i++){
for(let j = 0;j<m; j++){
for(let k =0;k<m; k++ ){
matrix[i][j] += a[i][k]* b[k][j]
}
}
}
return matrix
}