#include<fstream.h>
int t=0,v[1000],i,n,max,ok,k;
int main()
{
ifstream f("operatii.in");
ofstream g("operatii.out");
f>>n;
for(i=0;i<n;i++)f>>v[i];
while(!t)
 {t=1;
 for(i=0;i<n;i++)if(v[i]>max)max=v[i];
 for(i=0;i<n;i++){ok=0;while(max==v[i]){v[i]--;ok=1;i++;}if(ok)k++;}
 for(i=0;i<n;i++)if(v[i]){t=0;break;}
 max=0;}
g<<k;
f.close();
g.close();
return 0;
}