Matrix Calculation in C++: Sum of the Second Diagonal

using namespace std;
#include< stdio.h>
#include< stdlib.h>
#include < iostream>
#include < time.h>

int somme_diagonale(int **M,int n){
int sum=0;
for(int i = 0 ; i < n ; i++){
sum += M[i][n-i-1];
}
return sum;
}
void display(int** matte, int N, int M){
for(int i = 0; i < N; i++) {
for(int j = 0; j < M; j++) {
Cost < < Mat[i][j];
Cost < < "\t";
}
Cost < < "\n";
}
Cost < < "\n";
}
int main()
{
int n=3;
int** M = new int* [ n ];
for (int i=0; i < n; i++)
M[i] = new int[ n ];
srand(time(NULL));
for(int i=0; i< n; i++)
for(int j=0; j< n; j++)
M[i][j] =rand()%10;
display(M,n,n);
printf("sum of the second diagonal: %d\n",somme_diagonale(M,n));
return 0;

}