90分，WA一个点，求助！

#include<bits/stdc++.h>
using namespace std;
int n,m;
int a[105][105],f[105][105];
int main(){
    freopen("snow.in","r",stdin);
    freopen("snow.out","w",stdout);
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            scanf("%d",&a[i][j]);
            f[i][j]=1;
        }
    }
    int ans=100;
    while(ans--){
        for(int i=1;i<=n;i++){
            for(int j=1;j<=m;j++){
                if(a[i][j+1]<a[i][j]&&j<m){
                    f[i][j]=max(f[i][j],f[i][j+1]+1);
                }
                if(a[i][j-1]<a[i][j]&&j>1){
                    f[i][j]=max(f[i][j],f[i][j-1]+1);
                }
                if(a[i-1][j]<a[i][j]&&i>1){
                    f[i][j]=max(f[i][j],f[i-1][j]+1);
                }
                if(a[i+1][j]<a[i][j]&&i<n){
                    f[i][j]=max(f[i][j],f[i+1][j]+1);
                }
            }
        }
    }
    ans=0;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            ans=max(ans,f[i][j]);
        }
    }
    cout<<ans<<endl;
}